Sample records for fermi gamma-ray space

  1. The Animated Gamma-ray Sky Revealed by the Fermi Gamma-ray Space Telescope

    ScienceCinema (OSTI)

    Isabelle Grenier

    2010-01-08T23:59:59.000Z

    The Fermi Gamma-ray Space Telescope has been observing the sky in gamma-rays since August 2008.  In addition to breakthrough capabilities in energy coverage (20 MeV-300 GeV) and angular resolution, the wide field of view of the Large Area Telescope enables observations of 20% of the sky at any instant, and of the whole sky every three hours. It has revealed a very animated sky with bright gamma-ray bursts flashing and vanishing in minutes, powerful active galactic nuclei flaring over hours and days, many pulsars twinkling in the Milky Way, and X-ray binaries shimmering along their orbit. Most of these variable sources had not been seen by the Fermi predecessor, EGRET, and the wealth of new data already brings important clues to the origin of the high-energy emission and particles powered by the compact objects. The telescope also brings crisp images of the bright gamma-ray emission produced by cosmic-ray interactions in the interstellar medium, thus allowing to measure the cosmic nuclei and electron spectra across the Galaxy, to weigh interstellar clouds, in particular in the dark-gas phase. The telescope sensitivity at high energy will soon provide useful constraints on dark-matter annihilations in a variety of environments. I will review the current results and future prospects of the Fermi mission.

  2. Fundamental physics in space with the Fermi Gamma-ray Space Telescope

    E-Print Network [OSTI]

    Luca Baldini for the Fermi LAT Collaboration

    2011-01-09T23:59:59.000Z

    Successfully launched in June 2008, the Fermi Gamma-ray Space Telescope, formerly named GLAST, has been observing the high-energy gamma-ray sky with unprecedented sensitivity for more than two years, opening a new window on a wide variety of exotic astrophysical objects. This paper is a short overview of the main science highlights, aimed at non-specialists, with emphasis on those which are more directly connected with the study of fundamental physics---particularly the search for signals of new physics in the diffuse gamma-ray emission and in the cosmic radiation and the study of Gamma-Ray Burst as laboratories for testing possible violations of the Lorentz invariance.

  3. The Search for Dark Matter with the Fermi Gamma Ray Space Telescope

    SciTech Connect (OSTI)

    Bloom, Elliott (SLAC) [SLAC

    2011-03-30T23:59:59.000Z

    The Fermi Gamma-Ray Space Telescope has been scanning the gamma ray sky since it was launched by NASA in June 2008 and has a mission lifetime goal of 10 years. Largely due to our particle physics heritage, one of the main physics topics being studied by the Fermi LAT Collaboration is the search for dark matter via indirect detection. My talk will review the progress of these studies, something on how the LAT detector enables them, and expectations for the future. I will discuss both gamma-ray and (electron + positron) searches for dark matter, and some resulting theoretical implications.

  4. Fermi Gamma-ray Space Telescope: High-Energy Results from the First Year

    E-Print Network [OSTI]

    Peter F. Michelson; William B. Atwood; Steven Ritz

    2010-11-02T23:59:59.000Z

    The Fermi Gamma-ray Space Telescope (Fermi) was launched on June 11, 2008 and began its first year sky survey on August 11, 2008. The Large Area Telescope (LAT), a wide field-of-view pair-conversion telescope covering the energy range from 20 MeV to more than 300 GeV, is the primary instrument on Fermi. While this review focuses on results obtained with the LAT, the Gamma-ray Burst Monitor (GBM) complements the LAT in its observations of transient sources and is sensitive to X-rays and gamma-rays with energies between 8 keV and 40 MeV. During the first year in orbit, the Fermi LAT has observed a large number of sources that include active galaxies, pulsars, compact binaries, globular clusters, supernova remnants, as well as the Sun, the Moon and the Earth. The GBM and LAT together have uncovered surprising characteristics in the high-energy emission of gamma-ray bursts (GRBs) that have been used to set significant new limits on violations of Lorentz invariance. The Fermi LAT has also made important new measurements of the Galactic diffuse radiation and has made precise measurements of the spectrum of cosmic-ray electrons and positrons from 20 GeV to 1 TeV.

  5. Fermi Observations of Gamma-ray Bursts

    SciTech Connect (OSTI)

    Ohno, Masanori [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

    2010-10-15T23:59:59.000Z

    The gamma-ray emission mechanism of Gamma-ray bursts (GRBs) are still unknown. Fermi Gamma-ray Space Telescope successfully detected high-energy (> 100 MeV) emission from 17 GRBs since its launch. Fermi revealed the distinct temporal behaviors and extra spectral component from high-energy emission. These new observational results are driving many theoretical implications, such as leptonic, hadronic and afterglow origin. The highest energy photon detected by Fermi gives a constraint on the bulk Lorentz factor of the ultra-relativistic jets of GRBs. The impact of the Fermi GRB observations extends not only to the GRB-related issues but also to the outside GRB physics, such as quantum gravity and model of the extra galactic background light.

  6. Gamma-Ray Burst observations with Fermi

    E-Print Network [OSTI]

    Bissaldi, Elisabetta; Omodei, Nicola; Vianello, Giacomo; von Kienlin, Andreas

    2015-01-01T23:59:59.000Z

    After seven years of science operation, the Fermi mission has brought great advances in the study of Gamma-ray Bursts (GRBs). Over 1600 GRBs have been detected by the Gamma-ray Burst Monitor, and more than 100 of these are also detected by the Large Area Telescope above 30 MeV. We will give an overview of these observations, presenting the common properties in the GRB temporal and spectral behavior at high energies. We will also highlight the unique characteristics of some individual bursts. The main physical implications of these results will be discussed, along with open questions regarding GRB modeling in their prompt and temporally-extended emission phases.

  7. Discovery of Pulsations from the Pulsar J0205 6449 in SNR 3C 58 with the Fermi Gamma-Ray Space Telescope

    SciTech Connect (OSTI)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, Marco; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, William B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, Ronaldo; /INFN, Pisa; Berenji, Bijan; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Blandford, Roger D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, Elliott D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, Anders W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bouvier, A.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Columbia U. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /NASA, Goddard /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /LPCE, Orleans /Montpellier U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Manchester U. /Montpellier U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

    2011-12-01T23:59:59.000Z

    We report the discovery of {gamma}-ray pulsations ({ge}0.1 GeV) from the young radio and X-ray pulsar PSR J0205 + 6449 located in the Galactic supernova remnant 3C 58. Data in the {gamma}-ray band were acquired by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope (formerly GLAST), while the radio rotational ephemeris used to fold {gamma}-rays was obtained using both the Green Bank Telescope and the Lovell telescope at Jodrell Bank. The light curve consists of two peaks separated by 0.49 {+-} 0.01 {+-} 0.01 cycles which are aligned with the X-ray peaks. The first {gamma}-ray peak trails the radio pulse by 0.08 {+-} 0.01 {+-} 0.01, while its amplitude decreases with increasing energy as for the other {gamma}-ray pulsars. Spectral analysis of the pulsed {gamma}-ray emission suggests a simple power law of index -2.1 {+-} 0.1 {+-} 0.2 with an exponential cutoff at 3.0{sub -0.7}{sup +1.1} {+-} 0.4 GeV. The first uncertainty is statistical and the second is systematic. The integral {gamma}-ray photon flux above 0.1 GeV is (13.7 {+-} 1.4 {+-} 3.0) x 10{sup -8} cm{sup -2} s{sup -1}, which implies for a distance of 3.2 kpc and assuming a broad fan-like beam a luminosity of 8.3 x 10{sup 34} erg s{sup -1} and an efficiency {eta} of 0.3%. Finally, we report a 95% upper limit on the flux of 1.7 x 10{sup -8} cm{sup -2} s{sup -1} for off-pulse emission from the object.

  8. Calibration Analyses and Efficiency Studies for the Anti Coincidence Detector on the Fermi Gamma Ray Space Telescope

    SciTech Connect (OSTI)

    Kachulis, Chris; /Yale U. /SLAC

    2011-06-22T23:59:59.000Z

    The Anti Coincidence Detector (ACD) on the Fermi Gamma Ray Space Telescope provides charged particle rejection for the Large Area Telescope (LAT). We use two calibrations used by the ACD to conduct three studies on the performance of the ACD. We examine the trending of the calibrations to search for damage and find a timescale over which the calibrations can be considered reliable. We also calculated the number of photoelectrons counted by a PMT on the ACD from a normal proton. Third, we calculated the veto efficiencies of the ACD for two different veto settings. The trends of the calibrations exhibited no signs of damage, and indicated timescales of reliability for the calibrations of one to two years. The number of photoelectrons calculated ranged from 5 to 25. Large errors in the effect of the energy spectrum of the charged particles caused these values to have very large errors of around 60 percent. Finally, the veto efficiencies were found to be very high at both veto values, both for charged particles and for the lower energy backsplash spectrum. The Anti Coincidence Detector (ACD) on the Fermi Gamma Ray Space Telescope is a detector system built around the silicon strip tracker on the Large Area Telescope (LAT). The purpose of the ACD is to provide charged particle rejection for the LAT. To do this, the ACD must be calibrated correctly in flight, and must be able to efficiently veto charged particle events while minimizing false vetoes due to 'backsplash' from photons in the calorimeter. There are eleven calibrations used by the ACD. In this paper, we discuss the use of two of these calibrations to preform three studies on the performance of the ACD. The first study examines trending of the calibrations to check for possible hardware degradation. The second study uses the calibrations to explore the efficiency of an on-board hardware veto. The third study uses the calibrations to calculate the number of photoelectrons seen by each PMT when a minimum ionizing particle is detected, which is a useful value for performing simulations.

  9. Classification of Fermi Gamma-RAY Bursts

    E-Print Network [OSTI]

    Horvath, I; Hakkila, J; Bagoly, Z; Preece, R D

    2015-01-01T23:59:59.000Z

    The Fermi GBM Catalog has been recently published. Previous classification analyses of the BATSE, RHESSI, BeppoSAX, and Swift databases found three types of gamma-ray bursts. Now we analyzed the GBM catalog to classify the GRBs. PCA and Multiclustering analysis revealed three groups. Validation of these groups, in terms of the observed variables, shows that one of the groups coincides with the short GRBs. The other two groups split the long class into a bright and dim part, as defined by the peak flux. Additional analysis is needed to determine whether this splitting is only a mathematical byproduct of the analysis or has some real physical meaning.

  10. Gamma-ray Sky Observed with Fermi Large Area Telescope

    E-Print Network [OSTI]

    Yamamoto, Hirosuke

    detection reported Flare activity reported via ATel Gamma Ray Bursts reported via GCN Giant MC imageGamma-ray Sky Observed with Fermi Large Area Telescope RESCEU Symposium on Astroparticle Physics) Measure the photon direction Identification of the gamma-ray shower 36 planes of Si strip detectors (228 m

  11. THE FIRST FERMI-LAT GAMMA-RAY BURST CATALOG

    SciTech Connect (OSTI)

    Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L. [Universitŕ di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bechtol, K.; Bloom, E. D. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bhat, P. N. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Bissaldi, E. [Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck (Austria); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bonnell, J.; Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bouvier, A., E-mail: nicola.omodei@stanford.edu, E-mail: giacomov@slac.stanford.edu [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); and others

    2013-11-01T23:59:59.000Z

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (?> 20 MeV) ?-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ?20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.

  12. Compton scattering in terrestrial gamma-ray flashes detected with the Fermi gamma-ray burst monitor

    E-Print Network [OSTI]

    Fitzpatrick, Gerard; McBreen, Sheila; Briggs, Michael S; Foley, Suzanne; Tierney, David; Chaplin, Vandiver L; Connaughton, Valerie; Stanbro, Matthew; Xiong, Shaolin; Dwyer, Joseph; Fishman, Gerald J; Roberts, Oliver J; von Kienlin, Andreas

    2015-01-01T23:59:59.000Z

    Terrestrial gamma-ray flashes (TGFs) are short intense flashes of gamma rays associated with lightning activity in thunderstorms. Using Monte Carlo simulations of the relativistic runaway electron avalanche (RREA) process, theoretical predictions for the temporal and spectral evolution of TGFs are compared to observations made with the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope. Assuming a single source altitude of 15 km, a comparison of simulations to data is performed for a range of empirically chosen source electron variation time scales. The data exhibit a clear softening with increased source distance, in qualitative agreement with theoretical predictions. The simulated spectra follow this trend in the data, but tend to underestimate the observed hardness. Such a discrepancy may imply that the basic RREA model is not sufficient. Alternatively, a TGF beam that is tilted with respect to the zenith could produce an evolution with source distance that is compatible with the da...

  13. Fermi Discovery of Gamma-Ray Emission from NGC 1275

    SciTech Connect (OSTI)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Asano, K.; /Tokyo Inst. Tech.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, Elliott D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle; Caliandro, G.A.; /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /SISSA, Trieste /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /ASDC, Frascati /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U.; /more authors..

    2009-05-15T23:59:59.000Z

    We report the discovery of high-energy (E > 100 MeV) {gamma}-ray emission from NGC 1275, a giant elliptical galaxy lying at the center of the Perseus cluster of galaxies, based on observations made with the Large Area Telescope (LAT) of the Fermi Gamma-ray Space Telescope. The positional center of the {gamma}-ray source is only {approx}3{prime} away from the NGC 1275 nucleus, well within the 95% LAT error circle of {approx}5{prime}. The spatial distribution of {gamma}-ray photons is consistent with a point source. The average flux and power-law photon index measured with the LAT from 2008 August 4 to 2008 December 5 are F{sub {gamma}} = (2.10 {+-} 0.23) x 10{sup -7} ph (>100 MeV) cm{sup -2} s{sup -1} and {Gamma} = 2.17 {+-} 0.05, respectively. The measurements are statistically consistent with constant flux during the four-month LAT observing period. Previous EGRET observations gave an upper limit of F{sub {gamma}} < 3.72 x 10{sup -8} ph (>100 MeV) cm{sup -2} s{sup -1} to the {gamma}-ray flux from NGC 1275. This indicates that the source is variable on timescales of years to decades, and therefore restricts the fraction of emission that can be produced in extended regions of the galaxy cluster. Contemporaneous and historical radio observations are also reported. The broadband spectrum of NGC 1275 is modeled with a simple one-zone synchrotron/synchrotron self-Compton model and a model with a decelerating jet flow.

  14. Sensitivity of the FERMI Detectors to Gamma-Ray Bursts from Evaporating Primordial Black Holes (PBHs)

    E-Print Network [OSTI]

    T. N. Ukwatta; Jane H. MacGibbon; W. C. Parke; K. S. Dhuga; S. Rhodes; A. Eskandarian; N. Gehrels; L. Maximon; D. C. Morris

    2010-03-23T23:59:59.000Z

    Primordial Black Holes (PBHs), which may have been created in the early Universe, are predicted to be detectable by their Hawking radiation. The Fermi Gamma-ray Space Telescope observatory offers increased sensitivity to the gamma-ray bursts produced by PBHs with an initial mass of $\\sim 5\\times 10^{14}$ g expiring today. PBHs are candidate progenitors of unidentified Gamma-Ray Bursts (GRBs) that lack X-ray afterglow. We propose spectral lag, which is the temporal delay between the high and low energy pulses, as an efficient method to identify PBH evaporation events with the Fermi Large Area Telescope (LAT).

  15. Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes

    SciTech Connect (OSTI)

    Abdo, A.A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; Ajello, M.; /SLAC; Anderson, B.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Taiwan, Natl. Taiwan U. /Ohio State U.; Bechtol, K.; /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; Blandford, R.D.; Bloom, E.D.; /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /SLAC; Bregeon, J.; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /Stockholm U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Padua U. /Naval Research Lab, Wash., D.C. /Udine U. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /INFN, Pisa /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /CENBG, Gradignan /CENBG, Gradignan /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Udine U. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Bari U. /INFN, Bari /INFN, Pisa /INFN, Bari /NASA, Goddard /Maryland U.; /more authors..

    2012-04-11T23:59:59.000Z

    The diffuse galactic {gamma}-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess {gamma}-ray emission {ge}1 GeV relative to diffuse galactic {gamma}-ray emission models consistent with directly measured CR spectra (the so-called 'EGRET GeV excess'). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse {gamma}-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10{sup o} {le} |b| {le} 20{sup o}. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic {gamma}-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.

  16. Pulse properties of terrestrial gamma-ray flashes detected by the Fermi Gamma-Ray Burst Monitor

    E-Print Network [OSTI]

    Foley, Suzanne; Briggs, Michael S; Connaughton, Valerie; Tierney, David; McBreen, Sheila; Dwyer, Joseph; Chaplin, Vandiver L; Bhat, P Narayana; Byrne, David; Cramer, Eric; Fishman, Gerald J; Xiong, Shaolin; Greiner, Jochen; Kippen, R Marc; Meegan, Charles A; Paciesas, William S; Preece, Robert D; von Kienlin, Andreas; Wilson-Hodge, Colleen

    2015-01-01T23:59:59.000Z

    The Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope has triggered on over 300 terrestrial gamma-ray flashes (TGFs) since its launch in June 2008. With 14 detectors, GBM collects on average ~100 counts per triggered TGF, enabling unprecedented studies of the time profiles of TGFs. Here we present the first rigorous analysis of the temporal properties of a large sample of TGFs (278), including the distributions of the rise and fall times of the individual pulses and their durations. A variety of time profiles are observed with 19 of TGFs having multiple pulses separated in time and 31 clear cases of partially overlapping pulses. The effect of instrumental dead time and pulse pileup on the temporal properties are also presented. As the observed gamma ray pulse structure is representative of the electron flux at the source, TGF pulse parameters are critical to distinguish between relativistic feedback discharge and lightning leader models. We show that at least 67% of TGFs at satellite ...

  17. Fermi GBM Observations of Terrestrial Gamma-ray Flashes

    SciTech Connect (OSTI)

    Briggs, Michael S. [CSPAR, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States)

    2011-09-21T23:59:59.000Z

    Terrestrial Gamma-ray Flashes are short pulses of energetic radiation associated with thunderstorms and lightning. While the Gamma-ray Burst Monitor (GBM) on Fermi was designed to observe gamma-ray bursts, its large BGO detectors are excellent for observing TGFs. Using GBM, TGF pulses are seen to either be symmetrical or have faster rise time than fall times. Some TGFs are resolved into double, partially overlapping pulses. Using ground-based radio observations of lightning from the World Wide Lightning Location Network (WWLLN), TGFs and their associated lightning are found to be simultaneous to {approx_equal}40 {mu} s. The lightning locations are typically within 300 km of the sub-spacecraft point.

  18. Fermi Observations of High-Energy Gamma-Ray Emission from GRB 080916C

    E-Print Network [OSTI]

    Moskalenko, Igor V.

    Collaborations* Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory through the Gamma-ray Burst Monitor (GBM) and the Large Area Telescope (LAT) (9). The GBM consists of 12

  19. NEW FERMI-LAT EVENT RECONSTRUCTION REVEALS MORE HIGH-ENERGY GAMMA RAYS FROM GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L. [Universita di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bregeon, J.; Pesce-Rollins, M.; Sgro, C.; Tinivella, M. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Chekhtman, A. [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); Cohen-Tanugi, J. [Laboratoire Univers et Particules de Montpellier, Universite Montpellier 2, CNRS/IN2P3, F-34095 Montpellier (France); Drlica-Wagner, A.; Omodei, N.; Rochester, L. S.; Usher, T. L. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Ra'anana 43537 (Israel); Longo, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Razzaque, S. [Department of Physics, University of Johannesburg, Auckland Park 2006 (South Africa); Zimmer, S., E-mail: melissa.pesce.rollins@pi.infn.it, E-mail: nicola.omodei@stanford.edu, E-mail: granot@openu.ac.il [Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden)

    2013-09-01T23:59:59.000Z

    Based on the experience gained during the four and a half years of the mission, the Fermi-LAT Collaboration has undertaken a comprehensive revision of the event-level analysis going under the name of Pass 8. Although it is not yet finalized, we can test the improvements in the new event reconstruction with the special case of the prompt phase of bright gamma-ray bursts (GRBs), where the signal-to-noise ratio is large enough that loose selection cuts are sufficient to identify gamma rays associated with the source. Using the new event reconstruction, we have re-analyzed 10 GRBs previously detected by the Large Area Telescope (LAT) for which an X-ray/optical follow-up was possible and found four new gamma rays with energies greater than 10 GeV in addition to the seven previously known. Among these four is a 27.4 GeV gamma ray from GRB 080916C, which has a redshift of 4.35, thus making it the gamma ray with the highest intrinsic energy ({approx}147 GeV) detected from a GRB. We present here the salient aspects of the new event reconstruction and discuss the scientific implications of these new high-energy gamma rays, such as constraining extragalactic background light models, Lorentz invariance violation tests, the prompt emission mechanism, and the bulk Lorentz factor of the emitting region.

  20. Pulsed Gamma-Rays From PSR J2021 3651 with the Fermi Large Area Telescope

    SciTech Connect (OSTI)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, Marco; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, William B.; /UC, Santa Cruz; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Battelino, Milan; /Royal Inst. Tech., Stockholm; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, Ronaldo; /INFN, Pisa; Berenji, Bijan; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, Elliott D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bogaert, G.; /Ecole Polytechnique; Borgland, Anders W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Columbia U. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /George Mason U. /Naval Research Lab, Wash., D.C. /IASF, Milan /IASF, Milan /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /LPCE, Orleans /Montpellier U. /Sonoma State U. /Royal Inst. Tech., Stockholm /Stockholm U. /ASI, Rome /NRAO, Charlottesville /Naval Research Lab, Wash., D.C. /INFN, Trieste /Pavia U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Manchester U. /Montpellier U. /Bari U. /INFN, Bari; /more authors..

    2011-11-30T23:59:59.000Z

    We report the detection of pulsed gamma-rays from the young, spin-powered radio pulsar PSR J2021+3651 using data acquired with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). The light curve consists of two narrow peaks of similar amplitude separated by 0.468 {+-} 0.002 in phase. The first peak lags the maximum of the 2 GHz radio pulse by 0.162 {+-} 0.004 {+-} 0.01 in phase. The integral gamma-ray photon flux above 100 MeV is (56 {+-} 3 {+-} 11) x 10{sup -8} cm{sup -2} s{sup -1}. The photon spectrum is well-described by an exponentially cut-off power law of the form dF/dE = kE{sup -{Gamma}}e{sup (-E/E{sub c})} where the energy E is expressed in GeV. The photon index is {Gamma} = 1.5 {+-} 0.1 {+-} 0.1 and the exponential cut-off is E{sub c} = 2.4 {+-} 0.3 {+-} 0.5 GeV. The first uncertainty is statistical and the second is systematic. The integral photon flux of the bridge is approximately 10% of the pulsed emission, and the upper limit on off-pulse gamma-ray emission from a putative pulsar wind nebula is < 10% of the pulsed emission at the 95% confidence level. Radio polarization measurements yield a rotation measure of RM = 524 {+-} 4 rad m{sup -2} but a poorly constrained magnetic geometry. Re-analysis of Chandra data enhanced the significance of the weak X-ray pulsations, and the first peak is roughly phase-aligned with the first gamma-ray peak. We discuss the emission region and beaming geometry based on the shape and spectrum of the gamma-ray light curve combined with radio and X-ray measurements, and the implications for the pulsar distance. Gamma-ray emission from the polar cap region seems unlikely for this pulsar.

  1. Pulsed Gamma-Rays From the Millisecond Pulsar J0030+0451 with the Fermi Large Area Telescope

    SciTech Connect (OSTI)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M. /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Battelino, M.; /Stockholm U., OKC /Royal Inst. Tech., Stockholm; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, Elliott D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /LPCE, Orleans /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U.; /more authors..

    2011-11-17T23:59:59.000Z

    We report the discovery of gamma-ray pulsations from the nearby isolated millisecond pulsar PSR J0030+0451 with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). This discovery makes PSR J0030+0451 the second millisecond pulsar to be detected in gamma-rays after PSR J0218+4232, observed by the EGRET instrument on the Compton Gamma Ray Observatory. The spin-down power {dot E} = 3.5 x 10{sup 33} ergs s{sup -1} is an order of magnitude lower than the empirical lower bound of previously known gamma-ray pulsars. The emission profile is characterized by two narrow peaks, respectively 0.07 {+-} 0.01 and 0.08 {+-} 0.02 wide, separated by 0.44 {+-} 0.02 in phase. The first gamma-ray peak falls 0.15 {+-} 0.01 after the main radio peak. The pulse shape is similar to that of the 'normal' gamma-ray pulsars. An exponentially cut-off power-law fit of the emission spectrum leads to an integral photon flux above 100 MeV of (6.76 {+-} 1.05 {+-} 1.35) x 10{sup -8} cm{sup -2} s{sup -1} with cut-off energy (1.7 {+-} 0.4 {+-} 0.5) GeV. Based on its parallax distance of (300 {+-} 90) pc, we obtain a gamma-ray efficiency L{sub {gamma}}/{dot E} {approx_equal} 15% for the conversion of spin-down energy rate into gamma-ray radiation, assuming isotropic emission.

  2. THE FERMI ALL-SKY VARIABILITY ANALYSIS: A LIST OF FLARING GAMMA-RAY SOURCES AND THE SEARCH FOR TRANSIENTS IN OUR GALAXY

    SciTech Connect (OSTI)

    Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Albert, A. [Department of Physics, Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States); Allafort, A.; Bechtol, K.; Blandford, R. D.; Bloom, E. D.; Bottacini, E. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Antolini, E.; Bonamente, E. [Dipartimento di Fisica, Universita degli Studi di Perugia, I-06123 Perugia (Italy); Baldini, L. [Universita di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bouvier, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Brigida, M. [Dipartimento di Fisica ''M. Merlin'' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: majello@slac.stanford.edu, E-mail: allafort@stanford.edu, E-mail: rolf.buehler@desy.de [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); and others

    2013-07-01T23:59:59.000Z

    In this paper, we present the Fermi All-sky Variability Analysis (FAVA), a tool to systematically study the variability of the gamma-ray sky measured by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. For each direction on the sky, FAVA compares the number of gamma-rays observed in a given time window to the number of gamma-rays expected for the average emission detected from that direction. This method is used in weekly time intervals to derive a list of 215 flaring gamma-ray sources. We proceed to discuss the 27 sources found at Galactic latitudes smaller than 10 Degree-Sign and show that, despite their low latitudes, most of them are likely of extragalactic origin.

  3. Fermi large area telescope detection of a break in the gamma-ray spectrum of the supernova remnant Cassiopeia A

    SciTech Connect (OSTI)

    Yuan, Yajie; Funk, Stefan; Lande, Joshua; Tibaldo, Luigi [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Jóhannesson, Gülauger [Science Institute, University of Iceland, IS-107 Reykjavik (Iceland); Uchiyama, Yasunobu, E-mail: yuanyj@stanford.edu, E-mail: funk@slac.stanford.edu, E-mail: joshualande@gmail.com, E-mail: uchiyama@slac.stanford.edu [3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501 (Japan)

    2013-12-20T23:59:59.000Z

    We report on observations of the supernova remnant Cassiopeia A in the energy range from 100 MeV to 100 GeV using 44 months of observations from the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. We perform a detailed spectral analysis of this source and report on a low-energy break in the spectrum at 1.72{sub ?0.89}{sup +1.35} GeV. By comparing the results with models for the gamma-ray emission, we find that hadronic emission is preferred for the GeV energy range.

  4. MODELING THE NON-RECYCLED FERMI GAMMA-RAY PULSAR POPULATION

    SciTech Connect (OSTI)

    Perera, B. B. P.; McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Cordes, J. M. [Astronomy Department and NAIC, Cornell University, Ithaca, NY 14853 (United States); Kerr, M. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Burnett, T. H. [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2013-10-10T23:59:59.000Z

    We use Fermi Gamma-ray Space Telescope detections and upper limits on non-recycled pulsars obtained from the Large Area Telescope (LAT) to constrain how the gamma-ray luminosity L{sub ?} depends on the period P and the period derivative P-dot . We use a Bayesian analysis to calculate a best-fit luminosity law, or dependence of L{sub ?} on P and P-dot , including different methods for modeling the beaming factor. An outer gap (OG) magnetosphere geometry provides the best-fit model, which is L{sub ?}?P{sup -a} P-dot {sup b} where a = 1.36 ± 0.03 and b = 0.44 ± 0.02, similar to but not identical to the commonly assumed L{sub ?}??( E-dot )?P{sup -1.5} P-dot {sup 0.5}. Given upper limits on gamma-ray fluxes of currently known radio pulsars and using the OG model, we find that about 92% of the radio-detected pulsars have gamma-ray beams that intersect our line of sight. By modeling the misalignment of radio and gamma-ray beams of these pulsars, we find an average gamma-ray beaming solid angle of about 3.7? for the OG model, assuming a uniform beam. Using LAT-measured diffuse fluxes, we place a 2? upper limit on the average braking index and a 2? lower limit on the average surface magnetic field strength of the pulsar population of 3.8 and 3.2 × 10{sup 10} G, respectively. We then predict the number of non-recycled pulsars detectable by the LAT based on our population model. Using the 2 yr sensitivity, we find that the LAT is capable of detecting emission from about 380 non-recycled pulsars, including 150 currently identified radio pulsars. Using the expected 5 yr sensitivity, about 620 non-recycled pulsars are detectable, including about 220 currently identified radio pulsars. We note that these predictions significantly depend on our model assumptions.

  5. CONSTRAINING THE HIGH-ENERGY EMISSION FROM GAMMA-RAY BURSTS WITH FERMI

    SciTech Connect (OSTI)

    Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M.; Bechtol, K.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R.; Cameron, R. A.; Charles, E. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bonamente, E.; Cecchi, C. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bouvier, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Caliandro, G. A., E-mail: jchiang@slac.stanford.edu, E-mail: kocevski@slac.stanford.edu, E-mail: moretti@particle.kth.se, E-mail: connauv@uah.edu, E-mail: valerie@nasa.gov, E-mail: michael.briggs@nasa.gov [Institut de Ciencies de l'Espai (IEEE-CSIC), Campus UAB, E-08193 Barcelona (Spain); Collaboration: Fermi Large Area Telescope Team; Fermi Gamma-ray Burst Monitor Team; and others

    2012-08-01T23:59:59.000Z

    We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the {nu}F{sub {nu}} spectra (E{sub pk}). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E{sub pk} than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to {gamma}{gamma} attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  6. Gamma-ray Bursts in Wavelet Space

    E-Print Network [OSTI]

    Z. Bagoly; I. Horvath; A. Meszaros; L. G. Balazs

    2005-08-31T23:59:59.000Z

    The gamma-ray burst's lightcurves have been analyzed using a special wavelet transformation. The applied wavelet base is based on a typical Fast Rise-Exponential Decay (FRED) pulse. The shape of the wavelet coefficients' total distribution is determined on the observational frequency grid. Our analysis indicates that the pulses in the long bursts' high energy channel lightcurves are more FRED-like than the lower ones, independently from the actual physical time-scale.

  7. Fermi-LAT Discovery of GeV Gamma-ray Emission from the Young Supernova Remnant Cassiopeia A

    SciTech Connect (OSTI)

    Abdo, A.A.

    2011-08-19T23:59:59.000Z

    We report on the first detection of GeV high-energy gamma-ray emission from a young supernova remnant with the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope. These observations reveal a source with no discernible spatial extension detected at a significance level of 12.2{sigma} above 500 MeV at a location that is consistent with the position of the remnant of the supernova explosion that occurred around 1680 in the Cassiopeia constellation - Cassiopeia A. The gamma-ray flux and spectral shape of the source are consistent with a scenario in which the gamma-ray emission originates from relativistic particles accelerated in the shell of this remnant. The total content of cosmic rays (electrons and protons) accelerated in Cas A can be estimated as W{sub CR} {approx_equal} (1-4) x 10{sup 49} erg thanks to the well-known density in the remnant assuming that the observed gamma-ray originates in the SNR shell(s). The magnetic field in the radio-emitting plasma can be robustly constrained as B {ge} 0.1 mG, providing new evidence of the magnetic field amplification at the forward shock and the strong field in the shocked ejecta.

  8. Fermi-LAT Discovery of Extended Gamma-Ray Emission in the Direction of Supernova Remnant W51C

    SciTech Connect (OSTI)

    Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Baring, M.G.; /Rice U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bouvier, A.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique /Washington U., Seattle /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /DAPNIA, Saclay /INFN, Perugia /Perugia U. /NASA, Goddard /NASA, Goddard /CSST, Baltimore /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Sonoma State U. /Stockholm U. /Stockholm U., OKC /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Ecole Polytechnique; /more authors..

    2012-03-30T23:59:59.000Z

    The discovery of bright gamma-ray emission coincident with supernova remnant (SNR) W51C is reported using the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. W51C is a middle-aged remnant ({approx}10{sup 4} yr) with intense radio synchrotron emission in its shell and known to be interacting with a molecular cloud. The gamma-ray emission is spatially extended, broadly consistent with the radio and X-ray extent of SNR W51C. The energy spectrum in the 0.2-50 GeV band exhibits steepening toward high energies. The luminosity is greater than 1 x 10{sup 36} erg s{sup -1} given the distance constraint of D > 5.5 kpc, which makes this object one of the most luminous gamma-ray sources in our Galaxy. The observed gamma-rays can be explained reasonably by a combination of efficient acceleration of nuclear cosmic rays at supernova shocks and shock-cloud interactions. The decay of neutral p mesons produced in hadronic collisions provides a plausible explanation for the gamma-ray emission. The product of the average gas density and the total energy content of the accelerated protons amounts to {bar n}{sub H} W{sub p} {approx_equal} 5 x 10{sup 51} (D/6 kpc){sup 2} erg cm{sup -3}. Electron density constraints from the radio and X-ray bands render it difficult to explain the LAT signal as due to inverse Compton scattering. The Fermi LAT source coincident with SNR W51C sheds new light on the origin of Galactic cosmic rays.

  9. Fermi LAT Observations of LS I +61 303: First Detection of an Orbital Modulation in GeV Gamma Rays

    SciTech Connect (OSTI)

    Abdo, A.A.; /Federal City Coll. /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Blandford, R.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /DAPNIA, Saclay /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /DAPNIA, Saclay /NASA, Goddard /CSST, Baltimore /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Pavia U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Grenoble, CEN; /more authors..

    2012-04-02T23:59:59.000Z

    This Letter presents the first results from the observations of LS I +61{sup o}303 using Large Area Telescope data from the Fermi Gamma-Ray Space Telescope between 2008 August and 2009 March. Our results indicate variability that is consistent with the binary period, with the emission being modulated at 26.6 {+-} 0.5 days. This constitutes the first detection of orbital periodicity in high-energy gamma rays (20 MeV-100 GeV, HE). The light curve is characterized by a broad peak after periastron, as well as a smaller peak just before apastron. The spectrum is best represented by a power law with an exponential cutoff, yielding an overall flux above 100 MeV of 0.82 {+-} 0.03(stat) {+-} 0.07(syst) 10{sup -6} ph cm{sup -2} s{sup -1}, with a cutoff at 6.3 {+-} 1.1(stat) {+-} 0.4(syst) GeV and photon index {Gamma} = 2.21 {+-} 0.04(stat) {+-} 0.06(syst). There is no significant spectral change with orbital phase. The phase of maximum emission, close to periastron, hints at inverse Compton scattering as the main radiation mechanism. However, previous very high-energy gamma ray (>100 GeV, VHE) observations by MAGIC and VERITAS show peak emission close to apastron. This and the energy cutoff seen with Fermi suggest that the link between HE and VHE gamma rays is nontrivial.

  10. Fermi Large Area Telescope observations of high-energy gamma-ray emission from behind-the-limb solar flares

    E-Print Network [OSTI]

    Pesce-Rollins, Melissa; Petrosian, Vahe'; Liu, Wei; da Costa, Fatima Rubio; Allafort, Alice

    2015-01-01T23:59:59.000Z

    Fermi-LAT >30 MeV observations have increased the number of detected solar flares by almost a factor of 10 with respect to previous space observations. These sample both the impulsive and long duration phases of GOES M and X class flares. Of particular interest is the recent detections of three solar flares whose position behind the limb was confirmed by the STEREO-B spacecraft. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources and implications for the particle acceleration mechanisms.

  11. Compton scattering effects on the duration of terrestrial gamma-ray flashes

    E-Print Network [OSTI]

    Pasko, Victor

    ; published 18 January 2012. [1] Terrestrial gamma-ray flashes (TGFs) are gamma-ray bursts detected from space) recently discovered by the gamma-ray burst monitor (GBM) aboard the Fermi Gamma-Ray Space Telescope. Introduction [2] Terrestrial gamma-ray flashes (TGFs) are bursts of high-energy photons originating from

  12. THE SECOND FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS

    SciTech Connect (OSTI)

    Abdo, A. A. [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Allafort, A.; Bloom, E. D.; Bottacini, E. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L. [Universitŕ di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Rice University, Department of Physics and Astronomy, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Belfiore, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bhattacharyya, B. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411 007 (India); Bissaldi, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, and Universitŕ di Trieste, I-34127 Trieste (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Brigida, M., E-mail: hartog@stanford.edu [Dipartimento di Fisica ''M. Merlin'' dell'Universitŕ e del Politecnico di Bari, I-70126 Bari (Italy); and others

    2013-10-01T23:59:59.000Z

    This catalog summarizes 117 high-confidence ?0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

  13. Gamma-Ray Emission in Dissipative Pulsar Magnetospheres: From Theory to Fermi Observations

    E-Print Network [OSTI]

    Constantinos Kalapotharakos; Alice K. Harding; Demosthenes Kazanas

    2014-07-27T23:59:59.000Z

    We compute the patterns of $\\gamma$-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed $\\gamma$-ray light-curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near Force-Free. Using these solutions, we generate model $\\gamma$-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles, under the influence of both the accelerating electric fields and curvature radiation-reaction. We further constrain our models using the observed dependence of the phase-lags between the radio and $\\gamma$-ray emission on the $\\gamma$-ray peak-separation. We perform a statistical comparison of our model radio-lag vs peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity; specifically, infinite conductivity interior to the light-cylinder and high but finite conductivity on the outside. In these models the $\\gamma$-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio-lags near the observed values and statistically best reproduce the observed light-curve phenomenology. Additionally, these models produce GeV photon cut-off energies.

  14. New pulsars detected in gamma-rays with the Fermi-LAT

    E-Print Network [OSTI]

    Laffon, H; Guillemot, L

    2015-01-01T23:59:59.000Z

    The Fermi Large Area Telescope (LAT) is a powerful pulsar detector, as demonstrated by the over one hundred objects in its second catalog of pulsars. Pass 8 is a new reconstruction and event selection strategy developed by the Fermi-LAT collaboration. Due to the increased acceptance at low energy, Pass 8 improves the pulsation detection sensitivity. Ten new pulsars rise above the 5 sigma threshold and are presented in this work, as well as one previously seen with the former Pass 7 reconstruction. More than 60$\\%$ of the known pulsars with spin-down power ($\\dot{E}$) greater than $10^{36}$ erg/s show pulsations in gamma-rays, as seen with the Fermi Large Area Telescope. Many non-detections of these energetic pulsars are thought to be a consequence of a high background level, or a large distance leading to a flux below the sensitivity limit of the instrument. The gamma-ray beams of the others probably miss the Earth. The new Pass 8 data now allows the detection of gamma ray pulsations from three of these high ...

  15. Analysis of Fermi Gamma-Ray Burst duration distribution

    E-Print Network [OSTI]

    Tarnopolski, Mariusz

    2015-01-01T23:59:59.000Z

    Two classes of GRBs, short and long, have been determined without any doubts, and are usually prescribed to different physical scenarios. A third class, intermediate in $T_{90}$ durations, has been reported to be present in the datasets of BATSE, Swift, RHESSI and possibly BeppoSAX. The latest release of $>1500$ GRBs observed by Fermi gives an opportunity to further investigate the duration distribution. The aim of this paper is to investigate whether a third class is present in the $\\log T_{90}$ distribution, or is it described by a bimodal distribution. A standard $\\chi^2$ fitting of a mixture of Gaussians is applied to 25 histograms with different binnings. Different binnings give various values of the fitting parameters, as well as the shape of the fitted curve. Among five statistically significant fits none is trimodal. Locations of the Gaussian components are in agreement with previous works. However, a trimodal distribution, understood in the sense of having three separated peaks, is not found for any ...

  16. GRB 090926A AND BRIGHT LATE-TIME FERMI LARGE AREA TELESCOPE GAMMA-RAY BURST AFTERGLOWS

    SciTech Connect (OSTI)

    Swenson, C. A.; Roming, P. W. A.; Vetere, L.; Kennea, J. A. [Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Maxham, A.; Zhang, B. B.; Zhang, B. [University of Nevada, Las Vegas, Box 454002, 4505 Maryland Parkway, Las Vegas, NV 89154 (United States); Schady, P. [Max-Planck-Institut fuer extraterrestrische Physik, Garching (Germany); Holland, S. T. [Universities Space Research Association, 10227 Wincopin Circle, Suite 500, Columbia, MD 21044 (United States); Kuin, N. P. M.; Oates, S. R.; De Pasquale, M. [The UCL Mullard Space Science Laboratory, Holmbury St Mary, Surrey, RH5 6NT (United Kingdom); Page, K. L., E-mail: cswenson@astro.psu.ed [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2010-07-20T23:59:59.000Z

    GRB 090926A was detected by both the Gamma-ray Burst Monitor and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. Swift follow-up observations began {approx}13 hr after the initial trigger. The optical afterglow was detected for nearly 23 days post trigger, placing it in the long-lived category. The afterglow is of particular interest due to its brightness at late times, as well as the presence of optical flares at T0+10{sup 5} s and later, which may indicate late-time central engine activity. The LAT has detected a total of 16 gamma-ray bursts; nine of these bursts, including GRB 090926A, also have been observed by Swift. Of the nine Swift-observed LAT bursts, six were detected by UVOT, with five of the bursts having bright, long-lived optical afterglows. In comparison, Swift has been operating for five years and has detected nearly 500 bursts, but has only seen {approx}30% of bursts with optical afterglows that live longer than 10{sup 5} s. We have calculated the predicted gamma-ray fluence, as would have been seen by the Burst Alert Telescope (BAT) on board Swift, of the LAT bursts to determine whether this high percentage of long-lived optical afterglows is unique, when compared to BAT-triggered bursts. We find that, with the exception of the short burst GRB 090510A, the predicted BAT fluences indicate that the LAT bursts are more energetic than 88% of all Swift bursts and also have brighter than average X-ray and optical afterglows.

  17. FERMI LIMIT ON THE NEUTRINO FLUX FROM GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Li Zhuo [Department of Astronomy and Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing (China); Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming (China)

    2013-06-20T23:59:59.000Z

    If gamma-ray bursts (GRBs) produce high-energy cosmic rays, neutrinos are expected to be generated in GRBs via photo-pion productions. However, we stress that the same process also generates electromagnetic (EM) emission induced by the secondary electrons and photons, and that the EM emission is expected to be correlated with neutrino flux. Using Fermi/Large Area Telescope results on gamma-ray flux from GRBs, the GRB neutrino emission is limited to be <20 GeV m{sup -2} per GRB event on average, which is independent of the unknown GRB proton luminosity. This neutrino limit suggests that IceCube, operating at full scale, requires stacking of more than 130 GRBs in order to detect one GRB muon neutrino.

  18. SWIFT X-RAY TELESCOPE MONITORING OF FERMI-LAT GAMMA-RAY SOURCES OF INTEREST

    SciTech Connect (OSTI)

    Stroh, Michael C.; Falcone, Abe D. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

    2013-08-15T23:59:59.000Z

    We describe a long-term Swift monitoring program of Fermi gamma-ray sources, particularly the 23 gamma-ray ''sources of interest''.We present a systematic analysis of the Swift X-Ray Telescope light curves and hardness ratios of these sources, and we calculate excess variability. We present data for the time interval of 2004 December 22 through 2012 August 31. We describe the analysis methods used to produce these data products, and we discuss the availability of these data in an online repository, which continues to grow from more data on these sources and from a growing list of additional sources. This database should be of use to the broad astronomical community for long-term studies of the variability of these objects and for inclusion in multiwavelength studies.

  19. Fermi Limit on the Neutrino Flux from Gamma-ray Bursts

    E-Print Network [OSTI]

    Zhuo Li

    2013-06-14T23:59:59.000Z

    If gamma-ray bursts (GRBs) produce high energy cosmic rays, neutrinos are expected to be generated in GRBs due to photo-pion productions. However we stress that the same process also generates electromagnetic (EM) emission induced by the production of secondary electrons and photons, and that the EM emission is expected to be correlated to the neutrino flux. Using the Fermi/LAT observational results on gamma-ray flux from GRBs, the GRB neutrino emission is limited to be below ~20 GeV/m^2 per GRB event on average, which is independent of the unknown GRB proton luminosity. This neutrino limit suggests that the full IceCube needs stacking more than 130 GRBs in order to detect one GRB muon neutrino.

  20. Observations of Gamma-ray Bursts with ASTRO-H and Fermi

    E-Print Network [OSTI]

    Ohno, M; Tashiro, M S; Ueno, H; Yonetoku, D; Sameshima, H; Takahashi, T; Seta, H; Mushotzky, R; Yamaoka, K

    2015-01-01T23:59:59.000Z

    ASTRO-H, the sixth Japanese X-ray observatory, which is scheduled to be launched by the end of Japanese fiscal year 2015 has a capability to observe the prompt emission from Gamma-ray Bursts (GRBs) utilizing BGO active shields for the soft gamma-ray detector (SGD). The effective area of the SGD shield detectors is very large and its data acquisition system is optimized for short transients such as short GRBs. Thus, we expect to perform more detailed time-resolved spectral analysis with a combination of ASTRO-H and Fermi LAT/GBM to investigate the gamma-ray emission mechanism of short GRBs. In addition, the environment of the GRB progenitor should be a remarkable objective from the point of view of the chemical evolution of high-z universe. If we can maneuver the spacecraft to the GRBs, we can perform a high-resolution spectroscopy of the X-ray afterglow of GRBs utilizing the onboard micro calorimeter and X-ray CCD camera.

  1. THE SECOND FERMI GBM GAMMA-RAY BURST CATALOG: THE FIRST FOUR YEARS

    SciTech Connect (OSTI)

    Von Kienlin, Andreas; Greiner, Jochen; Gruber, David [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Meegan, Charles A.; Bhat, P. N.; Briggs, Michael S.; Burgess, J. Michael; Chaplin, Vandiver; Connaughton, Valerie; Goldstein, Adam [University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Paciesas, William S.; Cleveland, William [Universities Space Research Association, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Bissaldi, Elisabetta [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Byrne, David; Fitzpatrick, Gerard; Foley, Suzanne [School of Physics, University College Dublin, Belfield, Stillorgan Road, Dublin 4 (Ireland); Collazzi, Andrew C. [Astrophysics Office, ZP 12, NASA-Marshall Space Flight Center, Huntsville, AL 35812 (United States); Gibby, Melissa; Giles, Misty [Jacobs Technology, Inc., Huntsville, AL 35806 (United States); Guiriec, Sylvain [NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States); and others

    2014-03-01T23:59:59.000Z

    This is the second of a series of catalogs of gamma-ray bursts (GRBs) observed with the Fermi Gamma-ray Burst Monitor (GBM). It extends the first two-year catalog by two more years, resulting in an overall list of 953 GBM triggered GRBs. The intention of the GBM GRB catalog is to provide information to the community on the most important observables of the GBM detected GRBs. For each GRB the location and main characteristics of the prompt emission, the duration, peak flux and fluence are derived. The latter two quantities are calculated for the 50-300 keV energy band, where the maximum energy release of GRBs in the instrument reference system is observed and also for a broader energy band from 10-1000 keV, exploiting the full energy range of GBMs low-energy detectors. Furthermore, information is given on the settings and modifications of the triggering criteria and exceptional operational conditions during years three and four in the mission. This second catalog is an official product of the Fermi GBM science team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.

  2. THE FERMI GBM GAMMA-RAY BURST SPECTRAL CATALOG: FOUR YEARS OF DATA

    SciTech Connect (OSTI)

    Gruber, David; Von Ahlefeld, Victoria Weller; Diehl, Roland; Greiner, Jochen; Von Kienlin, Andreas [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Goldstein, Adam; Bhat, P. Narayana; Briggs, Michael S.; Connaughton, Valerie [University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Bissaldi, Elisabetta [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Byrne, Dave; Fitzpatrick, Gerard; Foley, Suzanne [School of Physics, University College Dublin, Belfield, Stillorgan Road, Dublin 4 (Ireland); Cleveland, William H. [Universities Space Research Association, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Fishman, Gerald J.; Kouveliotou, Chryssa [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Gibby, Melissa; Giles, Misty M. [Jacobs Technology, Inc., Huntsville, AL (United States); Guiriec, Sylvain [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Van der Horst, Alexander J. [Astronomical Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); and others

    2014-03-01T23:59:59.000Z

    In this catalog we present the updated set of spectral analyses of gamma-ray bursts (GRBs) detected by the Fermi Gamma-Ray Burst Monitor during its first four years of operation. It contains two types of spectra, time-integrated spectral fits and spectral fits at the brightest time bin, from 943 triggered GRBs. Four different spectral models were fitted to the data, resulting in a compendium of more than 7500 spectra. The analysis was performed similarly but not identically to Goldstein et al. All 487 GRBs from the first two years have been re-fitted using the same methodology as that of the 456 GRBs in years three and four. We describe, in detail, our procedure and criteria for the analysis and present the results in the form of parameter distributions both for the observer-frame and rest-frame quantities. The data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.

  3. MAGNETICALLY AND BARYONICALLY DOMINATED PHOTOSPHERIC GAMMA-RAY BURST MODEL FITS TO FERMI-LAT OBSERVATIONS

    SciTech Connect (OSTI)

    Veres, Peter; Meszaros, Peter [Department of Astronomy and Astrophysics, Department of Physics, and Center for Particle and Gravitational Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)] [Department of Astronomy and Astrophysics, Department of Physics, and Center for Particle and Gravitational Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Zhang, Bin-Bin, E-mail: veresp@psu.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)] [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)

    2013-02-10T23:59:59.000Z

    We consider gamma-ray burst models where the radiation is dominated by a photospheric region providing the MeV Band spectrum, and an external shock region responsible for the GeV radiation via inverse Compton scattering. We parameterize the initial dynamics through an acceleration law {Gamma}{proportional_to}r {sup {mu}}, with {mu} between 1/3 and 1 to represent the range between an extreme magnetically dominated and a baryonically dominated regime, depending also on the magnetic field configuration. We compare these models to several bright Fermi-LAT bursts, and show that both the time-integrated and the time-resolved spectra, where available, can be well described by these models. We discuss the parameters which result from these fits, and discuss the relative merits and shortcomings of the two models.

  4. Search for Gamma-ray Production in Supernovae Located in a Dense Circumstellar Medium with the Fermi-LAT

    E-Print Network [OSTI]

    ,

    2015-01-01T23:59:59.000Z

    Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are predicted to accelerate cosmic rays in collisionless shocks and emit GeV gamma rays and TeV neutrinos on a time scale of several months. Here we summarize the results of the first systematic search for gamma-ray emission in Fermi-LAT data in the energy range from 100 MeV to 300 GeV from a large sample of SNe exploding in dense CSM. We search for a gamma-ray excess at the position of 147 SNe Type IIn in a one year time window after the optical peak time. In addition we combine the closest and optically brightest sources of our sample in a joint likelihood analysis in three different time windows (3, 6 and 12 months). No excess gamma-ray emission is found and limits on the gamma-ray luminosity and the ratio of gamma-ray to optical luminosity are presented.

  5. THE INTERPLANETARY NETWORK SUPPLEMENT TO THE FERMI GBM CATALOG OF COSMIC GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Hurley, K. [University of California, Berkeley, Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Pal'shin, V. D.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Mazets, E. P.; Svinkin, D. S. [Ioffe Physical Technical Institute, St. Petersburg 194021 (Russian Federation); Briggs, M. S.; Connaughton, V. [University of Alabama in Huntsville, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Meegan, C. [Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Goldsten, J. [Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723 (United States); Boynton, W.; Fellows, C.; Harshman, K. [University of Arizona, Department of Planetary Sciences, Tucson, AZ 85721 (United States); Mitrofanov, I. G.; Golovin, D. V.; Kozyrev, A. S.; Litvak, M. L.; Sanin, A. B. [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); Rau, A., E-mail: khurley@ssl.berkeley.edu [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany); and others

    2013-08-15T23:59:59.000Z

    We present Interplanetary Network (IPN) data for the gamma-ray bursts in the first Fermi Gamma-Ray Burst Monitor (GBM) catalog. Of the 491 bursts in that catalog, covering 2008 July 12 to 2010 July 11, 427 were observed by at least one other instrument in the nine-spacecraft IPN. Of the 427, the localizations of 149 could be improved by arrival time analysis (or {sup t}riangulation{sup )}. For any given burst observed by the GBM and one other distant spacecraft, triangulation gives an annulus of possible arrival directions whose half-width varies between about 0.'4 and 32 Degree-Sign , depending on the intensity, time history, and arrival direction of the burst, as well as the distance between the spacecraft. We find that the IPN localizations intersect the 1{sigma} GBM error circles in only 52% of the cases, if no systematic uncertainty is assumed for the latter. If a 6 Degree-Sign systematic uncertainty is assumed and added in quadrature, the two localization samples agree about 87% of the time, as would be expected. If we then multiply the resulting error radii by a factor of three, the two samples agree in slightly over 98% of the cases, providing a good estimate of the GBM 3{sigma} error radius. The IPN 3{sigma} error boxes have areas between about 1 arcmin{sup 2} and 110 deg{sup 2}, and are, on the average, a factor of 180 smaller than the corresponding GBM localizations. We identify two bursts in the IPN/GBM sample that did not appear in the GBM catalog. In one case, the GBM triggered on a terrestrial gamma flash, and in the other, its origin was given as ''uncertain''. We also discuss the sensitivity and calibration of the IPN.

  6. GRB 110709A, 111117A, AND 120107A: FAINT HIGH-ENERGY GAMMA-RAY PHOTON EMISSION FROM FERMI-LAT OBSERVATIONS AND DEMOGRAPHIC IMPLICATIONS

    SciTech Connect (OSTI)

    Zheng Weikang; Akerlof, Carl W.; McKay, Timothy A. [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109 (United States); Pandey, Shashi B. [Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263129 (India); Zhang Binbin [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Zhang Bing [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States); Sakamoto, Takanori, E-mail: zwk@umich.edu [Center for Research and Exploration in Space Science and Technology (CRESST), NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2012-09-01T23:59:59.000Z

    Launched on 2008 June 11, the Large Area Telescope (LAT) instrument on board the Fermi Gamma-ray Space Telescope has provided a rare opportunity to study high-energy photon emission from gamma-ray bursts (GRBs). Although the majority of such events (27) have been identified by the Fermi-LAT Collaboration, four were uncovered by using more sensitive statistical techniques. In this paper, we continue our earlier work by finding three more GRBs associated with high-energy photon emission, GRB 110709A, 111117A, and 120107A. To systematize our matched filter approach, a pipeline has been developed to identify these objects in nearly real time. GRB 120107A is the first product of this analysis procedure. Despite the reduced threshold for identification, the number of GRB events has not increased significantly. This relative dearth of events with low photon number prompted a study of the apparent photon number distribution. We find an extremely good fit to a simple power law with an exponent of -1.8 {+-} 0.3 for the differential distribution. As might be expected, there is a substantial correlation between the number of lower energy photons detected by the Gamma-ray Burst Monitor (GBM) and the number observed by LAT. Thus, high-energy photon emission is associated with some but not all of the brighter GBM events. Deeper studies of the properties of the small population of high-energy emitting bursts may eventually yield a better understanding of these entire phenomena.

  7. Time-resolved analysis of Fermi gamma-ray bursts with fast- and slow-cooled synchrotron photon models

    SciTech Connect (OSTI)

    Burgess, J. M.; Preece, R. D.; Connaughton, V.; Briggs, M. S.; Goldstein, A.; Bhat, P. N.; Paciesas, W. S.; Xiong, S. [University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Greiner, J.; Gruber, D.; Kienlin, A.; Rau, A. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Kouveliotou, C. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); McGlynn, S. [Exzellence Cluster "Universe," Technische Universitt Mnchen, Boltzmannstrasse 2, D-85748, Garching (Germany); Meegan, C. A. [Universities Space Research Association, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baring, M. G. [Rice University, Department of Physics and Astronomy, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Dermer, C. D. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Iyyani, S. [The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm (Sweden); Kocevski, D., E-mail: james.m.burgess@nasa.gov, E-mail: Rob.Preece@nasa.gov, E-mail: shabuiyyani@gmail.com, E-mail: baring@rice.edu [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); and others

    2014-03-20T23:59:59.000Z

    Time-resolved spectroscopy is performed on eight bright, long gamma-ray bursts (GRBs) dominated by single emission pulses that were observed with the Fermi Gamma-Ray Space Telescope. Fitting the prompt radiation of GRBs by empirical spectral forms such as the Band function leads to ambiguous conclusions about the physical model for the prompt radiation. Moreover, the Band function is often inadequate to fit the data. The GRB spectrum is therefore modeled with two emission components consisting of optically thin non-thermal synchrotron radiation from relativistic electrons and, when significant, thermal emission from a jet photosphere, which is represented by a blackbody spectrum. To produce an acceptable fit, the addition of a blackbody component is required in five out of the eight cases. We also find that the low-energy spectral index ? is consistent with a synchrotron component with ? = –0.81 ± 0.1. This value lies between the limiting values of ? = –2/3 and ? = –3/2 for electrons in the slow- and fast-cooling regimes, respectively, suggesting ongoing acceleration at the emission site. The blackbody component can be more significant when using a physical synchrotron model instead of the Band function, illustrating that the Band function does not serve as a good proxy for a non-thermal synchrotron emission component. The temperature and characteristic emission-region size of the blackbody component are found to, respectively, decrease and increase as power laws with time during the prompt phase. In addition, we find that the blackbody and non-thermal components have separate temporal behaviors as far as their respective flux and spectral evolutions.

  8. Fermi LAT Detection of Pulsed Gamma-Rays From the Vela-Like Pulsars PSR J1048-5832 and PSR J2229+6114

    SciTech Connect (OSTI)

    Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Baring, M.G.; /Rice U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Columbia U. /IASF, Milan /Milan Polytechnic /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /LPCE, Orleans /Montpellier U. /Stockholm U. /Stockholm U., OKC /INFN, Trieste /Bari U. /INFN, Bari /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /INFN, Trieste /Arecibo Observ. /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Bari U. /INFN, Bari /INFN, Bari /NASA, Goddard /Maryland U. /INFN, Perugia /Perugia U.; /more authors..

    2012-03-29T23:59:59.000Z

    We report the detection of {gamma}-ray pulsations ({ge}0.1 GeV) from PSR J2229+6114 and PSR J1048-5832, the latter having been detected as a low-significance pulsar by EGRET. Data in the {gamma}-ray band were acquired by the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope, while the radio rotational ephemerides used to fold the {gamma}-ray light curves were obtained using the Green Bank Telescope, the Lovell telescope at Jodrell Bank, and the Parkes Telescope. The two young radio pulsars, located within the error circles of the previously unidentified EGRET sources 3EG J1048-5840 and 3EG J2227+6122, present spin-down characteristics similar to the Vela pulsar. PSR J1048-5832 shows two sharp peaks at phases 0.15 {+-} 0.01 and 0.57 {+-} 0.01 relative to the radio pulse confirming the EGRET light curve, while PSR J2229+6114 presents a very broad peak at phase 0.49 {+-} 0.01. The {gamma}-ray spectra above 0.1 GeV of both pulsars are fit with power laws having exponential cutoffs near 3 GeV, leading to integral photon fluxes of (2.19 {+-} 0.22 {+-} 0.32) x 10{sup -7} cm{sup -2} s{sup -1} for PSR J1048-5832 and (3.77 {+-} 0.22 {+-} 0.44) x 10{sup -7} cm{sup -2} s{sup -1} for PSR J2229+6114. The first uncertainty is statistical and the second is systematic. PSR J1048-5832 is one of the two LAT sources which were entangled together as 3EG J1048-5840. These detections add to the growing number of young {gamma}-ray pulsars that make up the dominant population of GeV {gamma}-ray sources in the Galactic plane.

  9. Broad Line Radio Galaxies Observed with Fermi-LAT: The Origin of the GeV Gamma-Ray Emission

    SciTech Connect (OSTI)

    Kataoka, J.; /Waseda U., RISE; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.; Takahashi, Y.; /Waseda U., RISE; Cheung, C.C.; /Natl. Acad. Sci. /Naval Research Lab, Wash., D.C.; Hayashida, M.; /SLAC /Stanford U., HEPL /KIPAC, Menlo Park; Grandi, P.; /Bologna Observ.; Burnett, T.H.; /Washington U., Seattle; Celotti, A.; /SISSA, Trieste; Fegan, S.J.; Fortin, P.; /Ecole Polytechnique; Maeda, K.; Nakamori, T.; /Waseda U., RISE; Taylor, G.B.; /New Mexico U.; Tosti, G.; /INFN, Perugia /Perugia U.; Digel, S.W.; /SLAC /Stanford U., HEPL /KIPAC, Menlo Park; McConville, W.; /NASA, Goddard /Maryland U.; Finke, J.; /Naval Research Lab, Wash., D.C.; D'Ammando, F.; /IASF, Palermo /INAF, Rome

    2012-06-07T23:59:59.000Z

    We report on a detailed investigation of the {gamma}-ray emission from 18 broad line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope (LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed {gamma}-ray emission reveals in addition possible flux variability in both sources. No statistically significant {gamma}-ray detection of the other BLRGs was however found in the considered dataset. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in {gamma}-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the {gamma}-ray flux variability and a number of other arguments presented, indicate that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found none were detected in {gamma}-rays. A simple phenomenological hybrid model applied for the broad-band emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is {ge} 1% on average for BLRGs, while {le} 0.1% for Seyfert 1 galaxies.

  10. CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI

    SciTech Connect (OSTI)

    Arlen, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Aune, T.; Bouvier, A. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Byrum, K. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Cannon, A.; Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Cesarini, A.; Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Cui, W.; Feng, Q.; Finley, J. P. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Dumm, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Falcone, A. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Federici, S., E-mail: pohlmadq@gmail.com, E-mail: christoph.pfrommer@h-its.org [DESY, Platanenallee 6, D-15738 Zeuthen (Germany); and others

    2012-10-01T23:59:59.000Z

    Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) Multiplication-Sign 10{sup -8} photons m {sup -2} s {sup -1} (VERITAS, >220 GeV) and {approx}2 Multiplication-Sign 10{sup -6} photons m {sup -2} s {sup -1} (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be <16% from VERITAS data and <1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of {approx}(2-5.5) {mu}G, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark matter (DM) dominated, the VERITAS upper limits have been used to place constraints on the thermally averaged product of the total self-annihilation cross section and the relative velocity of the DM particles, ({sigma}v).

  11. FIVE NEW MILLISECOND PULSARS FROM A RADIO SURVEY OF 14 UNIDENTIFIED FERMI-LAT GAMMA-RAY SOURCES

    SciTech Connect (OSTI)

    Kerr, M. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Johnson, T. J. [National Academy of Sciences, Washington, DC 20001 (United States); Ferrara, E. C.; Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Guillemot, L.; Kramer, M. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Hessels, J. [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Johnston, S.; Keith, M.; Reynolds, J. E. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping, NSW 1710 (Australia); Ransom, S. M. [National Radio Astronomy Observatory (NRAO), Charlottesville, VA 22903 (United States); Ray, P. S.; Wood, K. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Sarkissian, J., E-mail: kerrm@stanford.edu, E-mail: fernando@astro.columbia.edu, E-mail: tyrel.j.johnson@gmail.com [CSIRO Parkes Observatory, Parkes, NSW 2870 (Australia)

    2012-03-20T23:59:59.000Z

    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Fermi Large Area Telescope sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR J0101-6422 (P = 2.57 ms, DM = 12 pc cm{sup -3}), we have detected {gamma}-ray pulsations and measured its proper motion. Its {gamma}-ray spectrum (a power law of {Gamma} = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and {gamma}-ray light curves challenge simple geometric models of emission. The high success rate of this survey-enabled by selecting {gamma}-ray sources based on their detailed spectral characteristics-and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known.

  12. Search for Early Gamma-ray Production in Supernovae Located in a Dense Circumstellar Medium with the Fermi LAT

    E-Print Network [OSTI]

    ,

    2015-01-01T23:59:59.000Z

    Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV gamma rays and TeV neutrinos on a time scale of several months. We perform the first systematic search for gamma-ray emission in Fermi LAT data in the energy range from 100 MeV to 300 GeV from the ensemble of 147 SNe Type IIn exploding in dense CSM. We search for a gamma-ray excess at each SNe location in a one year time window. In order to enhance a possible weak signal, we simultaneously study the closest and optically brightest sources of our sample in a joint-likelihood analysis in three different time windows (1 year, 6 months and 3 months). For the most promising source of the sample, SN 2010jl (PTF10aaxf), we repeat the analysis with an extended time window lasting 4.5 years. We do not find a significant excess in gamma rays for any individual source nor for the combined sources and provide model-independent flux upper limits for both cases. In addition, we de...

  13. Diffuse Pionic Gamma-Ray Emission from Large Scale Structures in the FERMI Era

    E-Print Network [OSTI]

    Aleksandra Dobardzic; Tijana Prodanovic

    2014-04-08T23:59:59.000Z

    For more than a decade now the complete origin of the diffuse gamma-ray emission background (EGRB) has been unknown. Major components like unresolved star-forming galaxies (making SFCR gamma-ray emission are weak (above the observed EGRB) in some case, in others, some of our models can provide a good fit to the observed EGRB. More importantly, we show that these large-scale shocks could still give an important contribution to the EGRB, especially at high energies. Future detections of cluster gamma-ray emission would help place tighter constraints on our models and give us a better insight into large-scale shocks forming around them.

  14. Gamma-Ray Bursts from Primordial Quark Objects in Space

    E-Print Network [OSTI]

    B. Anoushirvani; D. Enström; S. Fredriksson; J. Hansson; P. Ökvist; A. Nicolaidis; S. Ekelin

    1997-11-28T23:59:59.000Z

    We investigate the possibility that gamma-ray bursts originate in a concentric spherical shell with a given average redshift and find that this is indeed compatible with the data from the third BATSE (3B) catalog. It is also shown that there is enough freedom in the choice of unknown burst properties to allow even for extremely large distances to the majority of bursts. Therefore, we speculate about an early, and very energetic, origin of bursts, and suggest that they come from phase transitions in massive objects of pure quark matter, left over from the Big Bang.

  15. ARE ABELL CLUSTERS CORRELATED WITH GAMMA-RAY BURSTS? Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450; khurley@sunspot.ssl.berkeley.edu

    E-Print Network [OSTI]

    California at Berkeley, University of

    ARE ABELL CLUSTERS CORRELATED WITH GAMMA-RAY BURSTS? K. HURLEY Space Sciences Laboratory statistical evidence that gamma-ray burst (GRB) sources are correlated with Abell clusters, based on analyses -- gamma rays: bursts 1. INTRODUCTION A correlation between the positions of gamma-ray bursts (GRBs

  16. Non-thermal emission from Galaxy Clusters and future observations with the FERMI gamma-ray telescope and LOFAR

    E-Print Network [OSTI]

    G. Brunetti

    2008-10-03T23:59:59.000Z

    FERMI (formely GLAST) and LOFAR will shortly provide crucial information on the non-thermal components (relativistic particles and magnetic field) in galaxy clusters. After discussing observational facts that already put constraints on the properties and origin of non-thermal components, I will report on the emission spectrum from galaxy clusters as expected in the context of general calculations in which relativistic particles (protons and secondary electrons due to proton-proton collisions) interact with MHD turbulence generated in the cluster volume during cluster-cluster mergers. In this scenario (known as re-acceleration scenario) diffuse cluster-scale radio emission is produced in massive clusters during merging events, while gamma ray emission, at some level, is expected to be common in clusters. Expectations of interest for LOFAR and FERMI are also briefly discussed.

  17. Fermi-LAT gamma-ray anisotropy and intensity explained by unresolved Radio-Loud Active Galactic Nuclei

    E-Print Network [OSTI]

    Mattia Di Mauro; Alessandro Cuoco; Fiorenza Donato; Jennifer M. Siegal-Gaskins

    2014-12-02T23:59:59.000Z

    Radio-loud active galactic nuclei (AGN) are expected to contribute substantially to both the intensity and anisotropy of the isotropic gamma-ray background (IGRB). In turn, the measured properties of the IGRB can be used to constrain the characteristics of proposed contributing source classes. We consider individual subclasses of radio-loud AGN, including low-, intermediate-, and high-synchrotron-peaked BL Lacertae objects, flat-spectrum radio quasars, and misaligned AGN. Using updated models of the gamma-ray luminosity functions of these populations, we evaluate the energy-dependent contribution of each source class to the intensity and anisotropy of the IGRB. We find that collectively radio-loud AGN can account for the entirety of the IGRB intensity and anisotropy as measured by the Fermi Large Area Telescope (LAT). Misaligned AGN provide the bulk of the measured intensity but a negligible contribution to the anisotropy, while high-synchrotron-peaked BL Lacertae objects provide the dominant contribution to the anisotropy. In anticipation of upcoming measurements with the Fermi-LAT and the forthcoming Cherenkov Telescope Array, we predict the anisotropy in the broader energy range that will be accessible to future observations.

  18. Temporal variations in space-time and progenitors of gamma ray burst and millisecond pulsars

    E-Print Network [OSTI]

    Preston Jones

    2007-08-31T23:59:59.000Z

    A time varying space-time metric is shown to be a source of electromagnetic radiation. The post-Newtonian approximation is used as a realistic model of the connection between the space-time metric and a time varying gravitational potential. Large temporal variations in the metric from the coalescence of colliding black holes and neutron stars are shown to be possible progenitors of gamma ray burst and millisecond pulsars.

  19. Search for Gamma-Ray Emission from DES Dwarf Spheroidal Galaxy Candidates with Fermi-LAT Data

    E-Print Network [OSTI]

    :,; Albert, A; Bechtol, K; Wood, M; Strigari, L; Sanchez-Conde, M; Baldini, L; Essig, R; Cohen-Tanugi, J; Anderson, B; Bellazzini, R; Bloom, E D; Caputo, R; Cecchi, C; Charles, E; Chiang, J; Conrad, J; de Angelis, A; Funk, S; Fusco, P; Gargano, F; Giglietto, N; Giordano, F; Guiriec, S; Gustafsson, M; Kuss, M; Loparco, F; Lubrano, P; Mirabal, N; Mizuno, T; Morselli, A; Ohsugi, T; Orlando, E; Persic, M; Raino, S; Spada, F; Suson, D J; Zaharijas, G; Zimmer, S; Abbott, T; Allam, S; Balbinot, E; Bauer, A H; Benoit-Levy, A; Bernstein, R A; Bernstein, G M; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Rosell, A Carnero; Castander, F J; Covarrubias, R; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Cunha, C E; Eifler, T F; Estrada, J; Evrard, A E; Neto, A Fausti; Fernandez, E; Finley, D A; Flaugher, B; Frieman, J; Gaztanaga, E; Gerdes, D; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; Jain, B; James, D; Jeltema, T; Kent, S; Kron, R; Kuropatkin, N; Lahav, O; Li, T S; Luque, E; Maia, M A G; Makler, M; March, M; Marshall, J; Martini, P; Merritt, K W; Miller, C; Miquel, R; Mohr, J; Neilsen, E; Nord, B; Ogando, R; Peoples, J; Petravick, D; Pieres, A; Plazas, A A; Queiroz, A; Romer, A K; Roodman, A; Rykoff, E S; Sako, M; Sanchez, E; Santiago, B; Scarpine, V; Schubnell, M; Sevilla, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Tucker, D; Walker, A; Wechsler, R H; Wester, W; Williams, P; Yanny, B; Zuntz, J

    2015-01-01T23:59:59.000Z

    Due to their proximity, high dark matter content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of dark matter. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. We found no significant excesses of gamma-ray emission. Under the assumption that the DES candidates are dSphs with dark matter halo properties similar to the known dSphs, we computed individual and combined limits on the velocity-averaged dark matter annihilation cross section for these new targets. If confirmed, they will constrain the annihilation cross section to lie below the thermal relic cross section for dark matter particles with masses < 20 GeV annihilating via the b-bbar or tau+tau- channels.

  20. REVISITING THE LONG/SOFT-SHORT/HARD CLASSIFICATION OF GAMMA-RAY BURSTS IN THE FERMI ERA

    SciTech Connect (OSTI)

    Zhang Fuwen; Yan Jingzhi; Wei Daming [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Shao Lang, E-mail: fwzhang@pmo.ac.cn [Department of Physics, Hebei Normal University, Shijiazhuang 050016 (China)

    2012-05-10T23:59:59.000Z

    We perform a statistical analysis of the temporal and spectral properties of the latest Fermi gamma-ray bursts (GRBs) to revisit the classification of GRBs. We find that the bimodalities of duration and the energy ratio (E{sub peak}/Fluence) and the anti-correlation between spectral hardness (hardness ratio (HR), peak energy, and spectral index) and duration (T{sub 90}) support the long/soft-short/hard classification scheme for Fermi GRBs. The HR-T{sub 90} anti-correlation strongly depends on the spectral shape of GRBs and energy bands, and the bursts with the curved spectra in the typical BATSE energy bands show a tighter anti-correlation than those with the power-law spectra in the typical BAT energy bands. This might explain why the HR-T{sub 90} correlation is not evident for those GRB samples detected by instruments like Swift with a narrower/softer energy bandpass. We also analyze the intrinsic energy correlation for the GRBs with measured redshifts and well-defined peak energies. The current sample suggests E{sub p,rest} = 2455 Multiplication-Sign (E{sub iso}/10{sup 52}){sup 0.59} for short GRBs, significantly different from that for long GRBs. However, both the long and short GRBs comply with the same E{sub p,rest}-L{sub iso} correlation.

  1. Gamma Ray Bursts

    E-Print Network [OSTI]

    Peter Mészáros

    2012-04-12T23:59:59.000Z

    Gamma-ray bursts have been detected at photon energies up to tens of GeV. We review some recent developments in the X-ray to GeV photon phenomenology in the light of Swift and Fermi observations, and some of the theoretical models developed to explain them, with a view towards implications for C.T.A.

  2. SGR J1550-5418 BURSTS DETECTED WITH THE FERMI GAMMA-RAY BURST MONITOR DURING ITS MOST PROLIFIC ACTIVITY

    SciTech Connect (OSTI)

    Van der Horst, A. J.; Finger, M. H. [Universities Space Research Association, NSSTC, Huntsville, AL 35805 (United States); Kouveliotou, C. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Gorgone, N. M. [Connecticut College, New London, CT 06320 (United States); Kaneko, Y.; Goegues, E.; Lin, L. [Sabanc Latin-Small-Letter-Dotless-I University, Orhanl Latin-Small-Letter-Dotless-I -Tuzla, Istanbul 34956 (Turkey); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Guiriec, S.; Bhat, P. N.; Chaplin, V. L.; Goldstein, A. [University of Alabama, Huntsville, CSPAR, Huntsville, AL 35805 (United States); Granot, J. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Watts, A. L. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Bissaldi, E.; Gruber, D. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, 85748 Garching (Germany); Gehrels, N.; Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gibby, M. H.; Giles, M. M., E-mail: A.J.VanDerHorst@uva.nl [Jacobs Technology, Inc., Huntsville, AL (United States); and others

    2012-04-20T23:59:59.000Z

    We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in 2009 January, resulting in the largest uniform sample of temporal and spectral properties of SGR J1550-5418 bursts. We have used the combination of broadband and high time-resolution data provided with GBM to perform statistical studies for the source properties. We determine the durations, emission times, duty cycles, and rise times for all bursts, and find that they are typical of SGR bursts. We explore various models in our spectral analysis, and conclude that the spectra of SGR J1550-5418 bursts in the 8-200 keV band are equally well described by optically thin thermal bremsstrahlung (OTTB), a power law (PL) with an exponential cutoff (Comptonized model), and two blackbody (BB) functions (BB+BB). In the spectral fits with the Comptonized model, we find a mean PL index of -0.92, close to the OTTB index of -1. We show that there is an anti-correlation between the Comptonized E{sub peak} and the burst fluence and average flux. For the BB+BB fits, we find that the fluences and emission areas of the two BB functions are correlated. The low-temperature BB has an emission area comparable to the neutron star surface area, independent of the temperature, while the high-temperature BB has a much smaller area and shows an anti-correlation between emission area and temperature. We compare the properties of these bursts with bursts observed from other SGR sources during extreme activations, and discuss the implications of our results in the context of magnetar burst models.

  3. Lorentz violation from gamma-ray bursts

    E-Print Network [OSTI]

    Shu Zhang; Bo-Qiang Ma

    2014-06-18T23:59:59.000Z

    The constancy of light speed is a basic assumption in Einstein's special relativity, and consequently the Lorentz invariance is a fundamental symmetry of space-time in modern physics. However, it is speculated that the speed of light becomes energy-dependent due to the Lorentz invariance violation~(LV) in various new physics theories. We analyse the data of the energetic photons from the gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Space Telescope, and find more events to support the energy dependence in the light speed with both linear and quadratic form corrections. We provide two scenarios to understand all the new-released Pass~8 data of bright GRBs by the Fermi-LAT Collaboration, with predictions from such scenarios being testable by future detected GRBs.

  4. Gamma-Ray Bursts

    E-Print Network [OSTI]

    P. Meszaros

    2006-05-30T23:59:59.000Z

    Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models of the prompt gamma ray burst and its afterglow is reviewed.

  5. Gamma ray burst delay times probe the geometry of momentum space

    E-Print Network [OSTI]

    Laurent Freidel; Lee Smolin

    2011-03-29T23:59:59.000Z

    We study the application of the recently proposed framework of relative locality to the problem of energy dependent delays of arrival times of photons that are produced simultaneously in distant events such as gamma ray bursts. Within this framework, possible modifications of special relativity are coded in the geometry of momentum space. The metric of momentum space codes modifications in the energy momentum relation, while the connection on momentum space describes possible non-linear modifications in the laws of conservation of energy and momentum. In this paper, we study effects of first order in the inverse Planck scale, which are coded in the torsion and non-metricity of momentum space. We find that time delays of order Distance * Energies/m_p are coded in the non-metricity of momentum space. Current experimental bounds on such time delays hence bound the components of this tensor of order 1/m_p. We also find a new effect, whereby photons from distant sources can appear to arrive from angles slightly off the direction to the sources, which we call gravitational lensing. This is found to be coded into the torsion of momentum space.

  6. Dissecting the Gamma-Ray Background in Search of Dark Matter

    SciTech Connect (OSTI)

    Cholis, Ilias; Hooper, Dan; McDermott, Samuel D.

    2014-02-01T23:59:59.000Z

    Several classes of astrophysical sources contribute to the approximately isotropic gamma-ray background measured by the Fermi Gamma-Ray Space Telescope. In this paper, we use Fermi's catalog of gamma-ray sources (along with corresponding source catalogs at infrared and radio wavelengths) to build and constrain a model for the contributions to the extragalactic gamma-ray background from astrophysical sources, including radio galaxies, star-forming galaxies, and blazars. We then combine our model with Fermi's measurement of the gamma-ray background to derive constraints on the dark matter annihilation cross section, including contributions from both extragalactic and galactic halos and subhalos. The resulting constraints are competitive with the strongest current constraints from the Galactic Center and dwarf spheroidal galaxies. As Fermi continues to measure the gamma-ray emission from a greater number of astrophysical sources, it will become possible to more tightly constrain the astrophysical contributions to the extragalactic gamma-ray background. We project that with 10 years of data, Fermi's measurement of this background combined with the improved constraints on the astrophysical source contributions will yield a sensitivity to dark matter annihilations that exceeds the strongest current constraints by a factor of ~ 5 - 10.

  7. Time resolved spectroscopy of SGR J1550–5418 bursts detected with Fermi/gamma-ray burst monitor

    SciTech Connect (OSTI)

    Younes, G. [Universities Space Research Association, 6767 Old Madison Pike, Suite 450, Huntsville, AL 35806 (United States); Kouveliotou, C.; Collazzi, A. [Astrophysics Office, ZP 12, NASA-Marshall Space Flight Center, Huntsville, AL 35812 (United States); Van der Horst, A. J.; Watts, A. L.; Huppenkothen, D.; Van der Klis, M.; Van Putten, T. [Astronomical Institute "Anton Pannekoek," University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raánana 43537 (Israel); Bhat, P. N.; Gorgone, N. [University of Alabama in Huntsville CSPAR, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Gehrels, N.; Mcenery, J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gö?ü?, E.; Kaneko, Y.; Lin, L. [Sabanc? University, Orhanl?-Tuzla, ?stanbul 34956 (Turkey); Gruber, D.; Von Kienlin, A. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, D-85748 Garching (Germany); Grunblatt, S. [University of Hawaii at Manoa, 2500 Campus Road, Honolulu, HI 96822 (United States); and others

    2014-04-10T23:59:59.000Z

    We report on a time-resolved spectroscopy of the 63 brightest bursts of SGR J1550–5418, detected with the Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms timescales to characterize the spectral evolution of the bursts. Using a Comptonized model, we find that the peak energy, E {sub peak}, anti-correlates with flux, while the low-energy photon index remains constant at ? – 0.8 up to a flux limit F ? 10{sup –5} erg s{sup –1} cm{sup –2}. Above this flux value, the E {sub peak}–flux correlation changes sign, and the index positively correlates with the flux reaching ?1 at the highest fluxes. Using a two blackbody model, we find that the areas and fluxes of the two emitting regions correlate positively. Further, we study here for the first time the evolution of the temperatures and areas as a function of flux. We find that the area–kT relation follows the lines of constant luminosity at the lowest fluxes, R {sup 2}?kT {sup –4}, with a break at the higher fluxes (F > 10{sup –5.5} erg s{sup –1} cm{sup –2}). The area of the high-kT component increases with the flux while its temperature decreases, which we interpret as being due to an adiabatic cooling process. The area of the low-kT component, on the other hand, appears to saturate at the highest fluxes, toward R {sub max} ? 30 km. Assuming that crust quakes are responsible for soft gamma repeater (SGR) bursts and considering R {sub max} as the maximum radius of the emitting photon-pair plasma fireball, we relate this saturation radius to a minimum excitation radius of the magnetosphere, and we put a lower limit on the internal magnetic field of SGR J1550–5418, B {sub int} ? 4.5 × 10{sup 15} G.

  8. Fermi Guest Investigator Program Cycle 2 Project Final Report Albedo Polarimetry of Gamma-Ray Bursts and Solar Flares with GBM

    SciTech Connect (OSTI)

    Kippen, Richard Marc [Los Alamos National Laboratory

    2012-08-27T23:59:59.000Z

    Several key properties of GRBs remain poorly understood and are difficult or even impossible to infer with the information currently being collected. Polarization measurements will probe the precise nature of the central engine. For solar flares, high-energy polarization measurements are expected to be useful in determining the beaming (or directivity) of solar flare electrons - a quantity that may provide important clues about electron acceleration and transport. We propose to investigate the viability of using the Fermi Gamma-ray Burst Monitor (GBM) to measure the polarization of GRBs and solar flares using the albedo photon flux. This approach was previously developed for use with BATSE data. We will conduct a careful study of this technique using a modified version of the GRESS simulation tools developed by the GBM team.

  9. Varying Faces of Photospheric Emission in Gamma-Ray Bursts

    E-Print Network [OSTI]

    Axelsson, M

    2015-01-01T23:59:59.000Z

    Among the more than 1000 gamma-ray bursts observed by the Fermi Gamma-ray Space Telescope, a large fraction show narrow and hard spectra inconsistent with non-thermal emission, signifying optically thick emission from the photosphere. However, only a few of these bursts have spectra consistent with a pure Planck function. We will discuss the observational features of photospheric emission in these GRBs as well as in the ones showing multi-component spectra. We interpret the observations in light of models of subphotospheric dissipation, geometrical broadening and multi-zone emission, and show what we can learn about the dissipation mechanism and properties of GRB jets.

  10. PoS(ICHEP2012)457 Search for Dark Matter with the Fermi Large Area

    E-Print Network [OSTI]

    Morselli, Aldo

    and astro-particle data? Since its launch in 2008, the Large Area Telescope, onboard of the Fermi Gamma-ray Space Telescope, has detected the largest amount of gamma rays in the 20MeV 300GeV energy range majority of the detected gamma-ray emission from the Galactic Center. Nevertheless a residual emission

  11. 51Gamma Ray Bubbles in the Milky Way NASA's Fermi Gamma-ray Space Telescope has unveiled a previously

    E-Print Network [OSTI]

    of these bubbles A) in kilograms? B) in solar mass units if 1 SMU = 2.0 x 10 30 kg? Problem 3 - Suppose of these bubbles A) in kilograms? B) in solar mass units if 1 SMU = 2.0 x 10 30 kg? Answer: A) Mass in one cubic) In solar mass units M= 1.4 x 10 27 kg x (1 SMU/2.0x 10 30 kg) = 1.1 x 10 10 solar masses. Problem 3

  12. Gamma Ray Bursts

    E-Print Network [OSTI]

    Stahl, Bennett

    2014-01-01T23:59:59.000Z

    Olson. “Observations of gamma-ray bursts of cosmic origin. ”E. Lingenfelter. “Gamma-ray bursts. ” Annual Review of652-654. Waxman, Eli. “Gamma-ray-burst afterglow: supporting

  13. The Universe Viewed in Gamma-Rays 1 Toward Ultra Short Gamma Ray Burst Ground Based De-

    E-Print Network [OSTI]

    Enomoto, Ryoji

    The Universe Viewed in Gamma-Rays 1 Toward Ultra Short Gamma Ray Burst Ground Based De- tection- liminary data taking started in November 2002. 1. Introduction Gamma-ray bursts observed with space Tcherenkovlightfromoneshower Few 100MeV gamma-rays Fig. 1. In an imaging telescope, -ray bursts should appear as a Cherenkov

  14. The Search for High Energy Extended Emission by Fermi-LAT from Swift-Localized Gamma-Ray Bursts

    SciTech Connect (OSTI)

    Chiang, J.; /Stanford U., HEPL /SLAC; Racusin, J.L.; /NASA, Goddard

    2012-05-01T23:59:59.000Z

    The brighter Fermi-LAT bursts have exhibited emission at energies >0.1 GeV that persists as late as {approx}2 ks after the prompt phase has nominally ended. This so-called 'extended emission' could arise from continued activity of the prompt burst mechanism or it could be the start of a high energy afterglow component. The high energy extended emission seen by the LAT has typically followed a t{sup -}{gamma} power-law temporal decay where {gamma} {approx} 1.2-1.7 and has shown no strong indication of spectral evolution. In contrast, the prompt burst emission generally displays strong spectral variability and more complex temporal changes in the LAT band. This differing behavior suggests that the extended emission likely corresponds to an early afterglow phase produced by an external shock. In this study, we look for evidence of high energy extended emission from 145 Swift-localized GRBs that have occurred since the launch of Fermi. A majority of these bursts were either outside of the LAT field-of-view or were otherwise not detected by the LAT during the prompt phase. However, because of the scanning operation of the Fermi satellite, the long-lived extended emission of these bursts may be detectable in the LAT data on the {approx}few ks time scale. We will look for emission from individual bursts and will perform a stacking analysis in order to set bounds on this emission for the sample as a whole. The detection of such emission would have implications for afterglow models and for the overall energy budget of GRBs.

  15. Gamma ray generator

    DOE Patents [OSTI]

    Firestone, Richard B; Reijonen, Jani

    2014-05-27T23:59:59.000Z

    An embodiment of a gamma ray generator includes a neutron generator and a moderator. The moderator is coupled to the neutron generator. The moderator includes a neutron capture material. In operation, the neutron generator produces neutrons and the neutron capture material captures at least some of the neutrons to produces gamma rays. An application of the gamma ray generator is as a source of gamma rays for calibration of gamma ray detectors.

  16. Solar Gamma Rays Powered by Secluded Dark Matter

    E-Print Network [OSTI]

    Brian Batell; Maxim Pospelov; Adam Ritz; Yanwen Shang

    2009-10-08T23:59:59.000Z

    Secluded dark matter models, in which WIMPs annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the solar system, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.

  17. Short Gamma-Ray Bursts with Extended Emission Observed with Swift/BAT and Fermi/GBM

    E-Print Network [OSTI]

    Kaneko, Y; Gogus, E; Lin, L

    2015-01-01T23:59:59.000Z

    Some short GRBs are followed by longer extended emission, lasting anywhere from ~10 to ~100 s. These short GRBs with extended emission (EE) can possess observational characteristics of both short and long GRBs (as represented by GRB 060614), and the traditional classification based on the observed duration places some of them in the long GRB class. While GRBs with EE pose a challenge to the compact binary merger scenario, they may therefore provide an important link between short and long duration events. To identify the population of GRBs with EE regardless of their initial classifications, we performed a systematic search of short GRBs with EE using all available data (up to February 2013) of both Swift/BAT and Fermi/GBM. The search identified 16 BAT and 14 GBM detected GRBs with EE, several of which are common events observed with both detectors. We investigated their spectral and temporal properties for both the spikes and the EE, and examined correlations among these parameters. Here we present the resul...

  18. 2009 Fermi Symposium, Washington, D.C., Nov. 2-5 1 Photon dispersion in causal sets

    E-Print Network [OSTI]

    Simić, Slobodan N.

    of light may be observable in Fermi time- and energy-tagged data on variable sources, such as gamma-ray by the Fermi Gamma Ray Space Telescope [1]. The expectation from general considerations [2] is that the scale bursts (GRB) and active galactic nuclei (AGN). We describe a method to compute the size of this effect

  19. GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES

    SciTech Connect (OSTI)

    Storm, Emma M.; Jeltema, Tesla E.; Profumo, Stefano [Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2012-08-20T23:59:59.000Z

    Star formation in galaxies is observed to be associated with gamma-ray emission, presumably from non-thermal processes connected to the acceleration of cosmic-ray nuclei and electrons. The detection of gamma rays from starburst galaxies by the Fermi Large Area Telescope (LAT) has allowed the determination of a functional relationship between star formation rate and gamma-ray luminosity. Since star formation is known to scale with total infrared (8-1000 {mu}m) and radio (1.4 GHz) luminosity, the observed infrared and radio emission from a star-forming galaxy can be used to quantitatively infer the galaxy's gamma-ray luminosity. Similarly, star-forming galaxies within galaxy clusters allow us to derive lower limits on the gamma-ray emission from clusters, which have not yet been conclusively detected in gamma rays. In this study, we apply the functional relationships between gamma-ray luminosity and radio and IR luminosities of galaxies derived by the Fermi Collaboration to a sample of the best candidate galaxy clusters for detection in gamma rays in order to place lower limits on the gamma-ray emission associated with star formation in galaxy clusters. We find that several clusters have predicted gamma-ray emission from star formation that are within an order of magnitude of the upper limits derived in Ackermann et al. based on non-detection by Fermi-LAT. Given the current gamma-ray limits, star formation likely plays a significant role in the gamma-ray emission in some clusters, especially those with cool cores. We predict that both Fermi-LAT over the course of its lifetime and the future Cerenkov Telescope Array will be able to detect gamma-ray emission from star-forming galaxies in clusters.

  20. Spectral Lags of Gamma-Ray Bursts from Primordial Black Hole (PBH) Evaporations

    E-Print Network [OSTI]

    T. N. Ukwatta; J. H. MacGibbon; W. C. Parke; K. S. Dhuga; A. Eskandarian; N. Gehrels; L. Maximon; D. C. Morris

    2009-08-14T23:59:59.000Z

    Primordial Black Holes (PBHs), which may have been created in the early Universe, are predicted to be detectable by their Hawking radiation. PBHs with an initial mass of 5.0 * 10^14 g should be expiring today with a burst of high energy particles. Evaporating PBHs in the solar neighborhood are candidate Gamma-Ray Bursts (GRBs) progenitors. We propose spectral lag, which is the temporal delay between the high energy photon pulse and the low energy photon pulse, as a possible method to detect PBH evaporation events with the Fermi Gamma-ray Space Telescope Observatory.

  1. Gamma Ray Bursts Sudden, intense flashes of gamma rays

    E-Print Network [OSTI]

    Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

    Gamma Ray Bursts #12;The Case Sudden, intense flashes of gamma rays come from nowhere and disappear with out a trace. Incredibly powerful: A single gamma ray burst is hundreds of times brighter a supernova #12;Who Vela (1960's) Looking for arms testing, found gamma ray bursts Compton Gamma Ray Observatory

  2. Simultaneous observations of optical lightning and terrestrial gamma ray flash from space

    E-Print Network [OSTI]

    Řstgaard, Nikolai

    3 Carthage College, Wisconsin, USA 4 SANSA Space Science, South Africa 5 University of KwaZulu-Natal, South Africa 6 Electrical and Computer Engineering Department, Duke University, North Carolina, USA 7 Energy Solar Spectroscopic Imager (RHESSI) more than twice as many TGFs24 than previously reported has

  3. Gamma-Ray Active Galactic Nucleus Type through Machine-Learning Algorithms

    E-Print Network [OSTI]

    Hassan, T; Contreras, J L; Oya, I

    2012-01-01T23:59:59.000Z

    The Fermi Gamma-ray Space Telescope is producing the most detailed inventory of the gamma-ray sky to date. Despite tremendous achievements approximately 25% of all Fermi extragalactic sources in the Second Fermi LAT Catalogue (2FGL) are listed as active galactic nuclei (AGN) of uncertain type. Typically, these are suspected blazar candidates without a conclusive optical spectrum or lacking spectroscopic observations. Here, we explore the use of machine-learning algorithms - Random Forests and Support Vector Machines - to predict specific AGN subclass based on observed gamma-ray spectral properties. After training and testing on identified/associated AGN from the 2FGL we find that 235 out of 269 AGN of uncertain type have properties compatible with gamma-ray BL Lacs and flat-spectrum radio quasars with accuracy rates of 85%. Additionally, direct comparison of our results with class predictions made following the infrared colour-colour space of Massaro et al. (2012) show that the agreement rate is over four-fif...

  4. Fermi Gamma-Ray Space Telescope: High-Energy Results From the First Year |

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOEThe Bonneville Power AdministrationField8,Dist. CategoryFebruaryFebruary 17,Time-Delay X-rayDots) -

  5. Gamma ray detector shield

    DOE Patents [OSTI]

    Ohlinger, R.D.; Humphrey, H.W.

    1985-08-26T23:59:59.000Z

    A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

  6. Microsoft Word - Fermi First Light Review_Final Corrections.doc

    Office of Scientific and Technical Information (OSTI)

    Fermi Gamma-ray Space Telescope: High-Energy Results from the First Year P F Michelson 1 , W B Atwood 2 , S Ritz 2 1. Department of Physics, Kavli Institute for Particle...

  7. Gamma-Ray Pulsar Studies With GLAST

    SciTech Connect (OSTI)

    Thompson, D.J.; /NASA, Goddard

    2011-11-23T23:59:59.000Z

    Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

  8. Searching for Overionized Plasma in the Gamma-ray Emitting Supernova Remnant G349.7$+$0.2

    E-Print Network [OSTI]

    Ergin, Tülün; Saha, Lab; Majumdar, Pratik; Gök, Fatma; Ercan, E Nihal

    2015-01-01T23:59:59.000Z

    G349.7$+$0.2 is a supernova remnant (SNR) expanding in a dense medium of molecular clouds and interacting with clumps of molecular material emitting gamma rays. We analyzed the gamma-ray data of Large Area Telescope on board Fermi Gamma Ray Space Telescope and detected G349.7$+$0.2 in the energy range of 0.2$-$300 GeV with a significance of $\\sim$13$\\sigma$ showing no extended morphology. Modeling of the gamma-ray spectrum revealed that the GeV gamma-ray emission dominantly originates from the decay of neutral pions, where the protons follow a broken power-law distribution with a spectral break at $\\sim$12 GeV. To search for features of radiative recombination continua in the eastern and western regions of the remnant, we analyzed the Suzaku data of G349.7$+$0.2 and found no evidence for overionized plasma. In this paper we discuss possible scenarios to explain the hadronic gamma-ray emission in G349.7$+$0.2 and the mixed morphology nature of this SNR.

  9. Neutrinos from Gamma Ray Bursts

    E-Print Network [OSTI]

    Karl Mannheim

    2000-10-18T23:59:59.000Z

    The observed fluxes of cosmic rays and gamma rays are used to infer the maximum allowed high-energy neutrino flux allowed for Gamma Ray Bursts (GRBs), following Mannheim, Protheroe, and Rachen (2000). It is shown that if GRBs produce the ultrahigh-energy cosmic rays, they should contribute (a) at least 10% of the extragalactic gamma ray background between 3 MeV and 30 GeV, contrary to their observed energy flux which is only a minute fraction of this flux, and (b) a cumulative neutrino flux a factor of 20 below the AMANDA (Neutrino 2000) limit on isotropic neutrinos. This could have two implications, either GRBs do not produce the ultrahigh energy cosmic rays or that the GRBs are strongly beamed and emit most of their power at energies well above 100 GeV implausibly increasing the energy requirements, but consistent with the marginal detections of a few low-redshift GRBs by MILAGRITO, HEGRA-AIROBICC, and the Tibet-Array. All crucial measurements to test the models will be available in the next few years. These are measurements of (i) high-energy neutrinos with AMANDA-ICECUBE or an enlarged ANTARES/NESTOR ocean detector, (ii) GRB redshifts from HETE-2 follow-up studies, and (iii) GRB spectra above 10 GeV with low-threshold imaging air Cherenkov telescopes such as MAGIC and the space telescopes AGILE and GLAST.

  10. Gamma-ray Albedo of the Moon

    SciTech Connect (OSTI)

    Moskalenko, Igor V.; Porter, Troy A.

    2007-06-14T23:59:59.000Z

    We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma-rays from the Moon is very steep with an effective cutoff around 3 GeV (600 MeV for the inner part of the Moon disc). Since it is the only (almost) black spot in the gamma-ray sky, it provides a unique opportunity for calibration of gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The albedo flux depends on the incident CR spectrum which changes over the solar cycle. Therefore, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo -rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the GLAST LAT to monitor the CR spectrum near the Earth beyond the lifetime of PAMELA.

  11. Gamma ray bursts in their historic context

    E-Print Network [OSTI]

    Trimble, V

    2004-01-01T23:59:59.000Z

    Gamma Ray Bursts In Their Historic Context Virginia TrimbleMD 20742 USA Abstract. Gamma ray bursts remained essentiallyalso applies to the gamma ray bursts. First, an observation

  12. THE EXTRAGALACTIC BACKGROUND LIGHT FROM THE MEASUREMENTS OF THE ATTENUATION OF HIGH-ENERGY GAMMA-RAY SPECTRUM

    SciTech Connect (OSTI)

    Gong Yan; Cooray, Asantha [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)

    2013-07-20T23:59:59.000Z

    The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features of the gamma-rays from blazars as seen by the Fermi Gamma-ray Space Telescope to explore the EBL flux density and constrain the EBL spectrum, star formation rate density (SFRD), and photon escape fraction from galaxies out to z = 6. Our results are basically consistent with the existing determinations of the quantities. We find a larger photon escape fraction at high redshifts, especially at z = 3, compared to the result from recent Ly{alpha} measurements. Our SFRD result is consistent with the data from both gamma-ray burst and ultraviolet (UV) observations in the 1{sigma} level. However, the average SFRD we obtain at z {approx}> 3 matches the gamma-ray data better than the UV data. Thus our SFRD result at z {approx}> 6 favors the fact that star formation alone is sufficiently high enough to reionize the universe.

  13. Testing No-Scale Supergravity with the Fermi Space Telescope LAT

    E-Print Network [OSTI]

    Tianjun Li; James A. Maxin; Dimitri V. Nanopoulos; Joel W. Walker

    2014-02-17T23:59:59.000Z

    We describe a methodology for testing No-Scale Supergravity by the LAT instrument onboard the Fermi Space Telescope via observation of gamma ray emissions from lightest supersymmetric (SUSY) neutralino annihilations. For our test vehicle we engage the framework of the supersymmetric grand unified model No-Scale Flipped $SU(5)$ with extra vector-like flippon multiplets derived from F-Theory, known as $\\cal{F}$-$SU(5)$. We show that through compression of the light stau and light bino neutralino mass difference, where internal bremsstrahlung (IB) photons give a dominant contribution, the photon yield from annihilation of SUSY dark matter can be elevated to a number of events potentially observable by the Fermi-LAT in the coming years. Likewise, the increased yield in No-Scale $\\cal{F}$-$SU(5)$ may also have rendered the existing observation of a 133 GeV monochromatic gamma ray line visible, if additional data should exclude systematic or statistical explanations. The question of intensity aside, No-Scale $\\cal{F}$-$SU(5)$ can indeed provide a natural weakly interacting massive particle (WIMP) candidate with a mass in the correct range to yield $\\gamma \\gamma$ and $\\gamma Z$ emission lines at $m_{\\chi} \\sim 133$ GeV and $m_{\\chi} \\sim 145$ GeV, respectively. Additionally, we elucidate the emerging empirical connection between recent Planck satellite data and No-Scale Supergravity cosmological models which mimic the Starobinsky model of inflation. Together, these experiments furnish rich alternate avenues for testing No-Scale $\\cal{F}$-$SU(5)$, and similarly structured models, the results of which may lend independent credence to observations made at the LHC.

  14. Local H~{\\sc i} emissivity measured with the {\\it Fermi}-LAT and implications for cosmic-ray spectra

    E-Print Network [OSTI]

    Casandjian, Jean-Marc

    2015-01-01T23:59:59.000Z

    Cosmic-ray (CR) electrons and nuclei interact with the Galactic interstellar gas and produce high-energy $\\gamma$ rays. The $\\gamma$-ray emission rate per hydrogen atom, called emissivity, provides a unique indirect probe of the CR flux. We present the measurement and the interpretation of the emissivity in the solar neighborhood for $\\gamma$-ray energy from 50~MeV to 50~GeV. We analyzed a subset of 4 years of observations from the Large Area Telescope (LAT) aboard the {\\it Fermi Gamma-ray Space Telescope} ({\\it Fermi}) restricted to absolute latitudes $10^oconversion factor $X_{CO}=(0.902\\pm0.007) \\times 10^{20}$ cm$^{-2}$ (K km s$^{-1}$)$^{-1}$ and the dust-to-gas ratio $X_{DUST}=(41.4\\pm0.3) \\times 10^{20}$ cm$^{-2}$ mag$^{-1}$. Moreover we detected for the first time $\\gamma$-ray emission from i...

  15. Detectability of Planck-Scale-Induced Blurring with Gamma-Ray Bursts

    E-Print Network [OSTI]

    Steinbring, Eric

    2015-01-01T23:59:59.000Z

    Microscopic fluctuations inherent to the fuzziness of spacetime at the Planck scale might accumulate in wavefronts propagating a cosmological distance and lead to noticeable blurring in an image of a pointlike source. Distant quasars viewed in the optical and ultraviolet with Hubble Space Telescope (HST} may show this weakly, and if real suggests a stronger effect should be seen for Gamma-Ray Bursts (GRBs) in X-rays and gamma-rays. Those telescopes, however, operate far from their diffraction limits. A description of how Planck-scale-induced blurring could be sensed at high energy, even with cosmic rays, while still agreeing with the HST results is discussed. It predicts dilated apparent source size and inflated uncertainties in positional centroids, effectively a threshold angular accuracy restricting knowledge of source location on the sky. These outcomes are found to be consistent with an analysis of the 10 highest-redshift GRB detections reported for the Fermi satellite. Confusion with photon cascade and ...

  16. On The Gamma-Ray Emission From Reticulum II and Other Dwarf Galaxies

    E-Print Network [OSTI]

    Hooper, Dan

    2015-01-01T23:59:59.000Z

    The recent discovery of ten new dwarf galaxy candidates by the Dark Energy Survey (DES) and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) could increase the Fermi Gamma-Ray Space Telescope's sensitivity to annihilating dark matter particles, potentially enabling a definitive test of the dark matter interpretation of the long-standing Galactic Center gamma-ray excess. In this paper, we compare the previous analyses of Fermi data from the directions of the new dwarf candidates (including the relatively nearby Reticulum II) and perform our own analysis, with the goal of establishing the statistical significance of any gamma-ray signal from these sources. We confirm the presence of an excess from Reticulum II, with a spectral shape that is compatible with the Galactic Center signal. The significance of this emission is greater than that observed from 99.84% of randomly chosen high-latitude blank-sky locations, corresponding to a local detection significance of 3.2 sigma. We improve upon th...

  17. Klein-Nishina effects on the high-energy gamma-ray emission of gamma-ray bursts

    SciTech Connect (OSTI)

    Wang Xiangyu [Department of Astronomy, Nanjing University, Nanjing 210093 (China) and Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093 (China)

    2010-10-15T23:59:59.000Z

    Prompt and long-lived high-energy (>100 MeV) gamma-ray emission has been detected by Fermi Large Area Telescope (LAT) recently from more than ten gamma-ray bursts. It has been suggested that such emission is produced by synchrotron radiation of electrons accelerated in internal and external shocks. Here we show that, during both the prompt and early afterglow phase, inverse-Compton (IC) scattering of these electrons with synchrotron photons are typically in the Klein-Nishina (KN) regime. For the prompt emission, the KN effect may strongly suppress the IC component, which is consistent with one single spectral component seen in some strong bursts, such as in GRB080916C and GRB090217. The KN inverse-Compton cooling may also affect the low-energy electron number distribution and hence results in a low-energy synchrotron photon spectrum harder than the standard fast-cooling spectrum n({nu}){proportional_to}{nu}{sup -3/2}. During the early afterglow, KN effect leads to a low Compton-Y parameter, which is generally less than a few in the first tens of seconds for a wide range of parameter space. Furthermore, we suggest that the KN effect can explain the somewhat faster than expected decay of the early-time high-energy emission observed in some GRBs.

  18. Analysis of Fermi Gamma-Ray Burst duration distribution II: No evidence for a third component in a mixture of skewed distributions

    E-Print Network [OSTI]

    Tarnopolski, Mariusz

    2015-01-01T23:59:59.000Z

    Two classes of GRBs have been identified thus far and are prescribed to different physical scenarios $-$ NS-NS or NS-BH mergers, and collapse of massive stars, for short and long GRBs, respectively. A third, intermediate in durations class, was suggested to be present in previous catalogs, such as BATSE and Swift, based on statistical tests regarding a mixture of two or three normal distributions. However, this might possibly not be an adequate model. This paper investigates whether the distribution of $\\log T_{90}$ from Fermi shows evidence for a third, intermediate, class of GRBs. Mixtures of standard Gaussians, skew-normal, sinh-arcsinh and alpha-skew-normal distributions are fitted using a maximum likelihood method. The preferred model is chosen based on the Akaike information criterion. It is found that mixtures of two skew-normal or two sinh-arcsinh distributions are more likely to describe the observed duration distribution than a mixture of three standard Gaussians. Based on statistical reasoning, exi...

  19. The 28th International Cosmic Ray Conference 1 X-ray and Gamma-ray Measurements

    E-Print Network [OSTI]

    Enomoto, Ryoji

    The 28th International Cosmic Ray Conference 1 X-ray and Gamma-ray Measurements Masaki Mori-ray and gamma-ray measurements, of the 28th International Cosmic Ray Conference. 1. Introduction Thick atmosphere of the earth forces direct observations of X-rays and gamma-rays on satellites in space

  20. On the Nature of the Gamma-ray Source 2FGL J1823.8 4312: The Discovery of a New Class of Extragalactic X-ray Sources

    SciTech Connect (OSTI)

    Massaro, Francesco

    2012-08-03T23:59:59.000Z

    One of the unsolved mysteries of gamma-ray astronomy concerns the nature of the unidentified gamma-ray sources. Recently, using the Second Fermi LAT source catalog (2FGL) and the Wide-field Infrared Survey Explorer (WISE) archive, we discovered that the WISE counterparts of gamma-ray blazars, a class of active galactic nuclei, delineate a region (the WISE Gamma-ray Strip) in the 3-dimensional infrared color space well separated from the locus of the other astronomical objects. Based on this result, we built an association procedure to recognize if there areWISE blazar candidates within the positional uncertainty region of the unidentified gamma-ray sources. Here we report on our analysis of 2FGL J1823.8+4312, a gamma-ray active galactic nucleus of uncertain type associated with the X-ray source 1RXS J182418.7+430954 according to the 2FGL, to verify whether it is a blazar. Applying our association method we found two sources with IR colors typical of gamma-ray blazars, located within the 99.9% confidence region of 2FGL J1823.8+4312: WISE J182352.33+431452.5 and WISE J182409.25+431404.7. Then we searched in the Chandra, NVSS and SDSS archival observations for their counterparts. We discovered that WISE J182352.33+431452.5, our preferred gamma-ray blazar candidate according to our WISE association procedure, is detected in the optical and in the X-rays but not in the radio, making it extremely unusual if it is a blazar. Given its enigmatic spectral energy distribution, we considered the possibility that it is a 'radio faint blazar' or the prototype of a new class of extragalactic sources, our conclusion is independent of whether WISE J182352.33+431452.5 is the actual counterpart of 2FGL J1823.8+4312.

  1. advanced gamma-ray detection: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    gamma-ray detection First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 117Fermi Detects Gamma-Rays from...

  2. Testing the millisecond pulsar scenario of the Galactic center gamma-ray excess with very high energy gamma-rays

    E-Print Network [OSTI]

    Qiang Yuan; Kunihito Ioka

    2015-02-09T23:59:59.000Z

    The recent analyses of the Fermi Large Area Telescope data show an extended GeV $\\gamma$-ray excess on top of the expected diffuse background in the Galactic center region, which can be explained with annihilating dark matter or a population of millisecond pulsars (MSPs). We propose to observe the very high energy $\\gamma$-rays for distinguishing the MSP scenario from the dark matter scenario. The GeV $\\gamma$-ray MSPs should release most energy to the relativistic $e^{\\pm}$ wind, which will diffuse in the Galaxy and radiate TeV $\\gamma$-rays through inverse Compton scattering and bremsstrahlung processes. By calculating the spectrum and spatial distribution, we show that such emission is detectable with the next generation very high energy $\\gamma$-ray observatory, the Cherenkov Telescope Array (CTA), under reasonable model parameters. It is essential to search for the multi-wavelength counterparts to the GeV $\\gamma$-ray excess for solving this mystery in the high energy universe.

  3. THE ORIGIN OF GAMMA RAYS FROM GLOBULAR CLUSTERS

    SciTech Connect (OSTI)

    Cheng, K. S. [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Chernyshov, D. O. [Moscow Institute of Physics and Technology, Institutskii lane, 141700 Moscow Region, Dolgoprudnii (Russian Federation); Dogiel, V. A. [I. E. Tamm Theoretical Physics Division of P. N. Lebedev Institute, Leninskii pr, 53, 119991 Moscow (Russian Federation); Hui, C. Y. [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of); Kong, A. K. H. [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)

    2010-11-10T23:59:59.000Z

    Fermi has detected gamma-ray emission from eight globular clusters (GCs). It is commonly believed that the energy sources of these gamma rays are millisecond pulsars (MSPs) inside GCs. Also it has been standard to explain the spectra of most Fermi Large Area Telescope pulsars including MSPs resulting from the curvature radiation (CR) of relativistic electrons/positrons inside the pulsar magnetosphere. Therefore, gamma rays from GCs are expected to be the collection of CR from all MSPs inside the clusters. However, the angular resolution is not high enough to pinpoint the nature of the emission. In this paper, we calculate the gamma rays produced by the inverse Compton (IC) scattering between relativistic electrons/positrons in the pulsar wind of MSPs in the GCs and background soft photons including cosmic microwave/relic photons, background star lights in the clusters, the galactic infrared photons, and the galactic star lights. We show that the gamma-ray spectrum from 47 Tucanae can be explained equally well by upward scattering of either the relic photons, the galactic infrared photons, or the galactic star lights, whereas the gamma-ray spectra from the other seven GCs are best fitted by the upward scattering of either the galactic infrared photons or the galactic star lights. We also find that the observed gamma-ray luminosity is correlated better with the combined factor of the encounter rate and the background soft photon energy density. Therefore, the IC scattering may also contribute to the observed gamma-ray emission from GCs detected by Fermi in addition to the standard CR process. Furthermore, we find that the emission region of high-energy photons from GCs produced by the IC scattering is substantially larger than the cores of GCs with a radius >10 pc. The diffuse radio and X-rays emitted from GCs can also be produced by the synchrotron radiation and IC scattering, respectively. We suggest that future observations including radio, X-rays, and gamma rays with energy higher than 10 GeV and better angular resolution can provide better constraints for the models.

  4. Real time gamma-ray signature identifier

    DOE Patents [OSTI]

    Rowland, Mark (Alamo, CA); Gosnell, Tom B. (Moraga, CA); Ham, Cheryl (Livermore, CA); Perkins, Dwight (Livermore, CA); Wong, James (Dublin, CA)

    2012-05-15T23:59:59.000Z

    A real time gamma-ray signature/source identification method and system using principal components analysis (PCA) for transforming and substantially reducing one or more comprehensive spectral libraries of nuclear materials types and configurations into a corresponding concise representation/signature(s) representing and indexing each individual predetermined spectrum in principal component (PC) space, wherein an unknown gamma-ray signature may be compared against the representative signature to find a match or at least characterize the unknown signature from among all the entries in the library with a single regression or simple projection into the PC space, so as to substantially reduce processing time and computing resources and enable real-time characterization and/or identification.

  5. The Gamma-ray Albedo of the Moon

    SciTech Connect (OSTI)

    Moskalenko, Igor V.; /Stanford U., HEPL; Porter, Troy A.; /UC, Santa Cruz

    2007-09-28T23:59:59.000Z

    We use the GEANT4 Monte Carlo framework to calculate the {gamma}-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of {gamma}-rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalization; this makes it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.

  6. TEMPORAL DECONVOLUTION STUDY OF LONG AND SHORT GAMMA-RAY BURST LIGHT CURVES

    SciTech Connect (OSTI)

    Bhat, P. N.; Briggs, Michael S.; Connaughton, Valerie; Paciesas, William; Burgess, Michael; Chaplin, Vandiver; Goldstein, Adam; Guiriec, Sylvain [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Kouveliotou, Chryssa; Fishman, Gerald [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Van der Horst, Alexander J.; Meegan, Charles A. [Center for Space Plasma and Aeronomic Research (CSPAR), Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Bissaldi, Elisabetta [Institute of Astro and Particle Physics, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck (Austria); Diehl, Roland; Foley, Suzanne; Greiner, Jochen; Gruber, David [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching (Germany); Fitzpatrick, Gerard [School of Physics, University College Dublin, Belfield, Stillorgan Road, Dublin 4 (Ireland); Gibby, Melissa; Giles, Misty M. [Jacobs Technology, Inc., Huntsville, AL 35806 (United States); and others

    2012-01-10T23:59:59.000Z

    The light curves of gamma-ray bursts (GRBs) are believed to result from internal shocks reflecting the activity of the GRB central engine. Their temporal deconvolution can reveal potential differences in the properties of the central engines in the two populations of GRBs which are believed to originate from the deaths of massive stars (long) and from mergers of compact objects (short). We present here the results of the temporal analysis of 42 GRBs detected with the Gamma-ray Burst Monitor onboard the Fermi Gamma-ray Space Telescope. We deconvolved the profiles into pulses, which we fit with lognormal functions. The distributions of the pulse shape parameters and intervals between neighboring pulses are distinct for both burst types and also fit with lognormal functions. We have studied the evolution of these parameters in different energy bands and found that they differ between long and short bursts. We discuss the implications of the differences in the temporal properties of long and short bursts within the framework of the internal shock model for GRB prompt emission.

  7. Gamma-Ray Burst Lines

    E-Print Network [OSTI]

    Michael S. Briggs

    1999-10-20T23:59:59.000Z

    The evidence for spectral features in gamma-ray bursts is summarized. As a guide for evaluating the evidence, the properties of gamma-ray detectors and the methods of analyzing gamma-ray spectra are reviewed. In the 1980's, observations indicated that absorption features below 100 keV were present in a large fraction of bright gamma-ray bursts. There were also reports of emission features around 400 keV. During the 1990's the situation has become much less clear. A small fraction of bursts observed with BATSE have statistically significant low-energy features, but the reality of the features is suspect because in several cases the data of the BATSE detectors appear to be inconsistent. Furthermore, most of the possible features appear in emission rather than the expected absorption. Analysis of data from other instruments has either not been finalized or has not detected lines.

  8. Gamma Ray Bursts and CETI

    E-Print Network [OSTI]

    Frank D. Smith Jr

    1993-02-10T23:59:59.000Z

    Gamma ray burst sources are isotropically distributed. They could be located at distances $\\sim 1000$ AU. (Katz \\cite{JK92}) GRB signals have many narrow peaks that are unresolved at the millisecond time resolution of existing observations. \\cite{JK87} CETI could use stars as gravitational lenses for interstellar gamma ray laser beam communication. Much better time resolution of GRB signals could rule out (or confirm?) the speculative hypothesis that GRB = CETI.

  9. Fermi-LAT Observation of Supernova Remnant S147

    SciTech Connect (OSTI)

    Katsuta, J.; Uchiyama, Y.; Tanaka, T.; /SLAC /KIPAC, Menlo Park; Tajima, H.; /SLAC /KIPAC, Menlo Park /Nagoya U., Solar-Terrestrial Environ. Lab.; Bechtol, K.; Funk, S.; Lande, J.; /SLAC /KIPAC, Menlo Park; Ballet, J.; /AIM, Saclay; Hanabata, Y.; /Hiroshima U.; Lemoine-Goumard, M.; /CENBG, Gradignan; Takahashi, T.; /JAXA, Sagamihara

    2012-08-17T23:59:59.000Z

    We present an analysis of gamma-ray data obtained with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region around SNR S147 (G180.0-1.7). A spatially extended gamma-ray source detected in an energy range of 0.2-10 GeV is found to coincide with SNR S147. We confirm its spatial extension at >5{sigma} confidence level. The gamma-ray flux is (3.8 {+-} 0.6) x 10{sup -8} photons cm{sup -2} s{sup -1}, corresponding to a luminosity of 1.3 x 10{sup 34} (d/1.3 kpc){sup 2} erg s{sup -1} in this energy range. The gamma-ray emission exhibits a possible spatial correlation with prominent H{alpha} filaments of S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538+2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral {pi} mesons produced through the proton-proton collisions in the filaments. Reacceleration of pre-existing CRs and subsequent adiabatic compression in the filaments is sufficient to provide the required energy density of high-energy protons.

  10. VERY HIGH ENERGY GAMMA RAY Tadashi KIFUNE

    E-Print Network [OSTI]

    Enomoto, Ryoji

    elementary particles as progenitor. The particle interaction includes also absorption of gamma rays through the present time. Detection of the relics of the earlier Universe, such as gamma rays from anti­based tech­ nique to detect TeV gamma rays. The current status of gamma ray astronomy in its growing stage

  11. VERY HIGH ENERGY GAMMA RAY Tadashi KIFUNE

    E-Print Network [OSTI]

    Enomoto, Ryoji

    particles as progenitor. The particle interaction includes also absorption of gamma rays through the process to detect TeV gamma rays. The current status of gamma ray astronomy in its growing stage is demonstrated of observation 2. Ground-based detection of VHE gamma rays from SN 1006 and Markaraina 501 The review of gamma

  12. Gamma ray bursts ROBERT S MACKAY

    E-Print Network [OSTI]

    Rourke, Colin

    Gamma ray bursts ROBERT S MACKAY COLIN ROURKE We propose that a gamma ray burst is a kinematic Gamma ray bursts are intense flashes of electromagnetic radiation of cosmic origin lasting from ten accepted mechanism. We propose that a gamma ray burst is simply a kinematic effect, namely the effect

  13. Are gamma-ray bursts cosmological?

    E-Print Network [OSTI]

    Horvath, I

    2015-01-01T23:59:59.000Z

    Gamma-ray burst sources are distributed with a high level of isotropy, which is compatible with either a cosmological origin or an extended Galactic halo origin. The brightness distribution is another indicator used to characterize the spatial distribution in distance. In this paper the author discusses detailed fits of the BATSE gamma-ray burst peak-flux distributions with Friedmann models taking into account possible density evolution and standard candle luminosity functions. A chi-square analysis is used to estimate the goodness of the fits and the author derives the significance level of limits on the density evolution and luminosity function parameters. Cosmological models provide a good fit over a range of parameter space which is physically reasonable

  14. The Universe Viewed in Gamma-Rays 1 Concept of new gamma ray detector

    E-Print Network [OSTI]

    Enomoto, Ryoji

    a sensitivity of a detector at TeV gamma ray range. This method was used for a non-imaging detector as XrayThe Universe Viewed in Gamma-Rays 1 Concept of new gamma ray detector Satoko Osone Institute Abstract We present a concept of a new gamma ray detector in order to observe undetected TeV gamma ray

  15. Gamma-RayGamma-Ray Bursts: from SwiftBursts: from Swift

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    Gamma-RayGamma-Ray Bursts: from SwiftBursts: from Swift to GLASTto GLAST Bing ZhangBing ZhangGehrels, et al), et al) #12;Gamma-ray bursts: the mostGamma-ray bursts: the most violent explosions fireball central photosphere internal external shocks engine (shocks) (reverse) (forward) gamma-ray UV

  16. A Search for Gamma-Ray Bursts and Pulsars, and the Application of Kalman Filters to Gamma-Ray Reconstruction

    E-Print Network [OSTI]

    B. B. Jones

    2002-02-04T23:59:59.000Z

    Part I describes the analysis of periodic and transient signals in EGRET data. A method to search for the transient flux from gamma-ray bursts independent of triggers from other gamma-ray instruments is developed. Several known gamma-ray bursts were independently detected, and there is evidence for a previously unknown gamma-ray burst candidate. Statistical methods using maximum likelihood and Bayesian inference are developed and implemented to extract periodic signals from gamma-ray sources in the presence of significant astrophysical background radiation. The analysis was performed on six pulsars and three pulsar candidates. The three brightest pulsars, Crab, Vela, and Geminga, were readily identified, and would have been detected independently in the EGRET data without knowledge of the pulse period. No significant pulsation was detected in the three pulsar candidates. Eighteen X-ray binaries were examined. None showed any evidence of periodicity. In addition, methods for calculating the detection threshold of periodic flux modulation were developed. The future hopes of gamma-ray astronomy lie in the development of the Gamma-ray Large Area Space Telescope, or GLAST. Part II describes the development and results of the particle track reconstruction software for a GLAST science prototype instrument beam test. The Kalman filtering method of track reconstruction is introduced and implemented. Monte Carlo simulations, very similar to those used for the full GLAST instrument, were performed to predict the instrumental response of the prototype. The prototype was tested in a gamma-ray beam at SLAC. The reconstruction software was used to determine the incident gamma-ray direction. It was found that the simulations did an excellent job of representing the actual instrument response.

  17. Cluster of Gamma-ray Bursts - Image of a Source. Catalog of Clusters (Sources) of Gamma-ray Bursts

    E-Print Network [OSTI]

    A. V. Kuznetsov

    2001-11-01T23:59:59.000Z

    The clusters of gamma-ray bursts are considered which are assumed to be images of the repeated gamma-ray burst (GRB) sources. It is shown, that localization of the cosmic gamma-ray burst sources (GBS) is determined by the clusters of GRBs. About 100 candidates in sources are presented in the form of the catalog, which is compiled relying on the base of the BATSE data up to middle of 2000. Gamma-ray bursts (from 5 to 13) of a cluster that display a source do not coincide in their position. The catalog table containing basic information about the GRB sources yields the possibility to research the GBS properties and their identification. The birth of GRBs in the clusters allows predicting the appearance of GRBs both in time and space. Most general properties of the supposed GRB sources are discussed. An attempt to compile the first GRB source catalog is made.

  18. And the remaining 22 photons: The development of gamma ray and gamma ray burst astronomy

    E-Print Network [OSTI]

    Trimble, V

    2005-01-01T23:59:59.000Z

    goblins and cosmic gamma ray bursts. Astrophysics and Spacelinear alignments of gamma-ray burst sources. Journal of theE.E. (eds. ), 1992. Gamma Ray Bursts. Cambridge, Cambridge

  19. Nuclear Instruments and Methods in Physics Research A 486 (2002) 623638 Simulation of the AGILE gamma-ray imaging detector

    E-Print Network [OSTI]

    2002-01-01T23:59:59.000Z

    gamma-ray imaging detector performance: Part II Veronica Coccoa,d, *, Francesco Longob,d , Marco Tavanic state physics instruments for cosmic gamma-ray detection in space will sub- stantially improve Detector (GRID) is devoted to optimal detection and imaging of cosmic gamma-rays. It is *Corresponding

  20. Nuclear Instruments and Methods in Physics Research A 486 (2002) 610622 Simulation of the AGILE gamma-ray imaging detector

    E-Print Network [OSTI]

    2002-01-01T23:59:59.000Z

    gamma-ray imaging detector performance: part I Francesco Longoa,d , Veronica Coccob,d, *, Marco Tavanic-photon background. The gamma-ray photon detection efficiency by the imaging GRID is simulated to be particularly of the Gamma-Ray Imaging Detector (GRID) being developed for the AGILE space astrophysics mission. The GRID

  1. Gamma-ray Albedo of Small Solar System Bodies

    SciTech Connect (OSTI)

    Moskalenko, I.V.

    2008-03-25T23:59:59.000Z

    We calculate the {gamma}-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the {gamma}-ray albedo for the Main Belt and KBOs strongly depends on the small-body mass spectrum of each system and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). If detected, it can be used to derive the mass spectrum of small bodies in the Main Belt and Kuiper Belt and to probe the spectrum of CR nuclei at close-to-interstellar conditions. The orbits of the Main Belt asteroids and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. Therefore, the {gamma}-ray emission by the Main Belt and Kuiper Belt has to be taken into account when analyzing weak {gamma}-ray sources close to the ecliptic. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center. For details of our calculations and references see [1].

  2. Neutrinos from Gamma Ray Bursts

    E-Print Network [OSTI]

    F. Halzen; G. Jaczko

    1996-02-07T23:59:59.000Z

    We show that the detection of neutrinos from a typical gamma ray burst requires a kilometer-scale detector. We argue that large bursts should be visible with the neutrino telescopes under construction. We emphasize the 3 techniques by which neutrino telescopes can perform this search: by triggering on i) bursts of muons from muon neutrinos, ii) muons from air cascades initiated by high energy gamma rays and iii) showers made by relatively low energy ($\\simeq 100\\,\\mev$) electron neutrinos. Timing of neutrino-photon coincidences may yield a measurement of the neutrino mass to order $10^{-5}$~eV, an interesting range in light of the solar neutrino anomaly.

  3. Fermi Large Area Telescope Operations: Progress Over 4 Years

    SciTech Connect (OSTI)

    Cameron, Robert A.; /SLAC

    2012-06-28T23:59:59.000Z

    The Fermi Gamma-ray Space Telescope was launched into orbit in June 2008, and is conducting a multi-year gamma-ray all-sky survey, using the main instrument on Fermi, the Large Area Telescope (LAT). Fermi began its science mission in August 2008, and has now been operating for almost 4 years. The SLAC National Accelerator Laboratory hosts the LAT Instrument Science Operations Center (ISOC), which supports the operation of the LAT in conjunction with the Mission Operations Center (MOC) and the Fermi Science Support Center (FSSC), both at NASA's Goddard Space Flight Center. The LAT has a continuous output data rate of about 1.5 Mbits per second, and data from the LAT are stored on Fermi and transmitted to the ground through TDRS and the MOC to the ISOC about 10 times per day. Several hundred computers at SLAC are used to process LAT data to perform event reconstruction, and gamma-ray photon data are subsequently delivered to the FSSC for public release with a few hours of being detected by the LAT. We summarize the current status of the LAT, and the evolution of the data processing and monitoring performed by the ISOC during the first 4 years of the Fermi mission, together with future plans for further changes to detected event data processing and instrument operations and monitoring.

  4. Gamma Ray Burst Neutrinos Probing Quantum Gravity

    E-Print Network [OSTI]

    M. C. Gonzalez-Garcia; F. Halzen

    2006-11-28T23:59:59.000Z

    Very high energy, short wavelength, neutrinos may interact with the space-time foam predicted by theories of quantum gravity. They would propagate like light through a crystal lattice and be delayed, with the delay depending on the energy. This will appear to the observer as a violation of Lorenz invariance. Back of the envelope calculations imply that observations of neutrinos produced by gamma ray bursts may reach Planck-scale sensitivity. We revisit the problem considering two essential complications: the imprecise timing of the neutrinos associated with their poorly understood production mechanism in the source and the indirect nature of their energy measurement made by high energy neutrino telescopes.

  5. Cooling of Accelerated Nucleons and Neutrino Emission in Gamma-Ray Bursts

    E-Print Network [OSTI]

    Katsuaki Asano

    2005-03-11T23:59:59.000Z

    Using Monte Carlo simulations, we demonstrate photopion production from Fermi-accelerated protons and the resulting neutrino production in gamma-ray bursts. Unless internal shocks occur at quite large distance from the center, ultra high-energy protons are depleted by photopion production and synchrotron radiation. Internal shocks at fiducial distance cause neutrino bursts, which accompany gamma-ray bursts originating from electromagnetic cascades.

  6. Light Curves of Swift Gamma Ray Bursts

    E-Print Network [OSTI]

    Paolo Cea

    2006-09-22T23:59:59.000Z

    Recent observations from the Swift gamma-ray burst mission indicate that a fraction of gamma ray bursts are characterized by a canonical behaviour of the X-ray afterglows. We present an effective theory which allows us to account for X-ray light curves of both (short - long) gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars.

  7. Pulsed Gamma-Ray-Burst Afterglows

    E-Print Network [OSTI]

    J. Middleditch

    2009-01-01T23:59:59.000Z

    provides a candidate for the central engine of the gamma-ray burst (GRB) mechanism, both long and short

  8. The Universe Viewed in Gamma-Rays 1 Properties of Gamma-ray Bursts Localized by

    E-Print Network [OSTI]

    Enomoto, Ryoji

    The Universe Viewed in Gamma-Rays 1 Properties of Gamma-ray Bursts Localized by the HETE-2 and localize Gamma-ray bursts (GRBs) in wide field of view. HETE-2 have been localized about 20 GRBs per year hours after the burst. 1. The High Energy Transient Explorer 2 Gamma-ray burst (GRB) is the most

  9. Fermi point in graphene as a monopole in momentum space

    E-Print Network [OSTI]

    M . A. Zubkov

    2011-12-15T23:59:59.000Z

    We consider the effective field theory of graphene monolayer with the Coulomb interaction between fermions taken into account. The gauge field in momentum space is introduced. The position of the Fermi point coincides with the position of the corresponding monopole. The procedure of extracting such monopoles during lattice simulations is suggested.

  10. The Diverse Environments of Gamma-Ray Bursts

    E-Print Network [OSTI]

    Perley, Daniel Alan

    2011-01-01T23:59:59.000Z

    Galaxies of Dark Gamma-Ray Bursts: Observational Constraintsof a Very Bright Gamma- Ray Burst in a Galactic Halo 3.11.3 Gamma-Ray Burst Classi?cation . . . . . . 1.4 Gamma-Ray

  11. Mon. Not. R. Astron. Soc. 415, 7782 (2011) doi:10.1111/j.1365-2966.2011.18648.x Is GeV emission from Gamma-Ray Bursts of external shock origin?

    E-Print Network [OSTI]

    Zhang, Bing

    2011-01-01T23:59:59.000Z

    from Gamma-Ray Bursts of external shock origin? Amanda Maxham, Bin-Bin Zhang and Bing Zhang Department February 22; in original form 2010 December 30 ABSTRACT Recent observations of Gamma-Ray Bursts (GRBs (080916C, 090510, 090902B and 090926A) jointly detected by Fermi LAT and Gamma-ray Burst Monitor (GBM

  12. Gamma-ray boxes from axion-mediated dark matter

    SciTech Connect (OSTI)

    Ibarra, Alejandro; Gehler, Sergio López; Pato, Miguel [Physik-Department T30d, Technische Universität München, James-Franck-Strasse, 85748 Garching (Germany); Lee, Hyun Min; Park, Wan-Il, E-mail: ibarra@tum.de, E-mail: hyun.min.lee@cern.ch, E-mail: sergio.lopez@ph.tum.de, E-mail: wipark@kias.re.kr, E-mail: miguel.pato@tum.de [School of Physics, KIAS, Seoul 130-722 (Korea, Republic of)

    2013-05-01T23:59:59.000Z

    We compute the gamma-ray output of axion-mediated dark matter and derive the corresponding constraints set by recent data. In such scenarios the dark matter candidate is a Dirac fermion that pair-annihilates into axions and/or scalars. Provided that the axion decays (at least partly) into photons, these models naturally give rise to a box-shaped gamma-ray spectrum that may present two distinct phenomenological behaviours: a narrow box, resembling a line at half the dark matter mass, or a wide box, spanning an extensive energy range up to the dark matter mass. Remarkably, we find that in both cases a sizable gamma-ray flux is predicted for a thermal relic without fine-tuning the model parameters nor invoking boost factors. This large output is in line with recent Fermi-LAT observations towards the galactic centre region and is on the verge of being excluded. We then make use of the Fermi-LAT and H.E.S.S. data to derive robust, model-independent upper limits on the dark matter annihilation cross section for the narrow and wide box scenarios. H.E.S.S. constraints, in particular, turn out to match the ones from Fermi-LAT at hundreds of GeV and extend to multi-TeV masses. Future ?erenkov telescopes will likely probe gamma-ray boxes from thermal dark matter relics in the whole multi-TeV range, a region hardly accessible to direct detection, collider searches and other indirect detection strategies.

  13. Spectral Analysis of the Crab Pulsar and Nebula with the Fermi Large Area Telescope

    E-Print Network [OSTI]

    ,

    2015-01-01T23:59:59.000Z

    The Crab Pulsar is a relatively young neutron star. The pulsar is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was observed on Earth in the year 1054. The Crab Pulsar has been extensively observed in the gamma-ray energy band by the Large Area Telescope (LAT), the main instrument onboard the Fermi Gamma-ray Space Telescope, during its first months of data taking. The LAT data have been used to reconstruct the fluxes and the energy spectra of the pulsed gamma-ray component and of the gamma-rays from the nebula. The results on the pulsed component are in good agreement with the previous measurement from EGRET, while the results on the nebula are consistent with the observations from Earth based telescopes.

  14. HYPERACCRETING BLACK HOLE AS GAMMA-RAY BURST CENTRAL ENGINE. I. BARYON LOADING IN GAMMA-RAY BURST JETS

    SciTech Connect (OSTI)

    Lei Weihua [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, 4505 Maryland Parkway, Box 454002, Las Vegas, NV 89154-4002 (United States); Liang Enwei, E-mail: leiwh@hust.edu.cn, E-mail: zhang@physics.unlv.edu [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning 530004 (China)

    2013-03-10T23:59:59.000Z

    A hyperaccreting stellar-mass black hole has been long speculated as the best candidate for the central engine of gamma-ray bursts (GRBs). Recent rich observations of GRBs by space missions such as Swift and Fermi pose new constraints on GRB central engine models. In this paper, we study the baryon-loading processes of a GRB jet launched from a black hole central engine. We consider a relativistic jet powered by {nu} {nu}-bar -annihilation or by the Blandford-Znajek (BZ) mechanism. We consider baryon loading from a neutrino-driven wind launched from a neutrino-cooling-dominated accretion flow. For a magnetically dominated BZ jet, we consider neutron drifting from the magnetic wall surrounding the jet and subsequent positron capture and proton-neutron inelastic collisions. The minimum baryon loads in both types of jet are calculated. We find that in both cases a more luminous jet tends to be more baryon poor. A neutrino-driven ''fireball'' is typically ''dirtier'' than a magnetically dominated jet, while a magnetically dominated jet can be much cleaner. Both models have the right scaling to interpret the empirical {Gamma}-L{sub iso} relation discovered recently. Since some neutrino-driven jets have too much baryon loading as compared with the data, we suggest that at least a good fraction of GRBs should have a magnetically dominated central engine.

  15. Gamma Ray Bursts from Minijets

    E-Print Network [OSTI]

    Nir J. Shaviv; Arnon Dar

    1994-07-14T23:59:59.000Z

    Striking similarities exist between high energy gamma ray emission from active galactic nuclei (AGN) and gamma ray bursts (GRBs). They suggest that GRBs are generated by inverse Compton scattering from highly relativistic electrons in transient jets. Such jets may be produced along the axis of an accretion disk formed around stellar black holes (BH) or neutron stars (NS) in BH-NS and NS-NS mergers and in accretion induced collapse of magnetized white dwarfs (WD) or neutron stars in close binary systems. Such events may produce the cosmological GRBs. Transient jets formed by single old magnetized neutron stars in an extended Galactic halo may produce a local population of GRBs. Here we show that jet production of GRBs by inverse Compton scattering can explain quite simply the striking correlations that exist between various temporal features of GRBs, their duration histogram, the power spectrum of their complex multipeak light curves, their power-law high energy spectra and other features of GRBs. Some additional predictions are made including the expected polarization of gamma-rays in the bursts.

  16. MODELING PHOTODISINTEGRATION-INDUCED TeV PHOTON EMISSION FROM LOW-LUMINOSITY GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Liu Xuewen [Physics Department, Sichuan University, Chengdu 610065 (China); Wu Xuefeng; Lu Tan, E-mail: astrolxw@gmail.com, E-mail: xfwu@pmo.ac.cn, E-mail: t.lu@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2012-05-15T23:59:59.000Z

    Ultra-high-energy cosmic-ray heavy nuclei have recently been considered as originating from nearby low-luminosity gamma-ray bursts that are associated with Type Ibc supernovae. Unlike the power-law decay in long duration gamma-ray bursts, the light curve of these bursts exhibits complex UV/optical behavior: shock breakout dominated thermal radiation peaks at about 1 day, and, after that, nearly constant emission sustained by radioactive materials for tens of days. We show that the highly boosted heavy nuclei at PeV energy interacting with the UV/optical photon field will produce considerable TeV photons via the photodisintegration/photo-de-excitation process. It was later predicted that a thermal-like {gamma}-ray spectrum peaks at about a few TeV, which may serve as evidence of nucleus acceleration. The future observations by the space telescope Fermi and by the ground atmospheric Cherenkov telescopes such as H.E.S.S., VERITAS, and MAGIC will shed light on this prediction.

  17. Afterglows as Diagnostics of Gamma Ray Burst Beaming

    E-Print Network [OSTI]

    James E. Rhoads

    1997-12-03T23:59:59.000Z

    If gamma ray bursts are highly collimated, radiating into only a small fraction of the sky, the energy requirements of each event may be reduced by several (up to 4 - 6) orders of magnitude, and the event rate increased correspondingly. The large Lorentz factors (Gamma > 100) inferred from GRB spectra imply relativistic beaming of the gamma rays into an angle 1/Gamma. We are at present ignorant of whether there are ejecta outside this narrow cone. Afterglows allow empirical tests of whether GRBs are well-collimated jets or spherical fireballs. The bulk Lorentz factor decreases and radiation is beamed into an ever increasing solid angle as the burst remnant expands. It follows that if gamma ray bursts are highly collimated, many more optical and radio transients should be observed without associated gamma rays than with them. In addition, a burst whose ejecta are beamed into angle zeta undergoes a qualitative change in evolution when Gamma < 1/zeta: Before this, Gamma ~ r^{-3/2}, while afterwards, Gamma decays exponentially with r. This change results in a potentially observable break in the afterglow light curve. Successful application of either test would eliminate the largest remaining uncertainty in the energy requirements and space density of gamma ray bursters.

  18. What Are Gamma-Ray Bursts -- The Unique Role of Very High Energy Gamma-Ray Observations

    E-Print Network [OSTI]

    Williams, D A; Baring, M G; Buckley, J; Connaughton, V; Coppi, P; Dermer, C; Digel, S; Dingus, B; Fryer, C; Gehrels, N; Granot, J; Horan, D; Katz, J I; Mészáros, P; Norris, J; Parkinson, P Saz; Peér, A; Razzaque, S; Sinnis, G; Wang, X Y; Weekes, T C; Zhang, B

    2009-01-01T23:59:59.000Z

    Gamma-ray bursts (GRBs) have been an enigma since their discovery forty years ago. However, considerable progress unraveling their mysteries has been made in recent years. Developments in observations, theory, and instrumentation have prepared the way so that the next decade can be the one in which we finally answer the question, "What are gamma-ray bursts?" This question encompasses not only what the progenitors are that produce the GRBs, but also how the enormous luminosity of the GRBs, concentrated in gamma rays, is achieved. Observations across the electromagnetic spectrum, from both the ground and space, will be required to fully tackle this important question. This white paper, mostly distilled from a recent study commissioned by the Division of Astrophysics of the American Physical Society, focuses on what very high energy (~100 GeV and above) gamma-ray observations can contribute. Very high energy gamma rays probe the most extreme high energy particle populations in the burst environment, testing mode...

  19. VERY HIGH ENERGY GAMMA RAYS FROM THE VELA PULSAR DIRECTION

    E-Print Network [OSTI]

    Enomoto, Ryoji

    VERY HIGH ENERGY GAMMA RAYS FROM THE VELA PULSAR DIRECTION T. Yoshikoshi1;2, T. Kifune2, S and Mathematical Physics, University of Adelaide, Adelaide, South Australia 5005, Australia 4Institute of SpaceDepartment of Physics, Kyoto University, Kyoto, Kyoto 606, Japan 8Solar-Terrestrial Environment Laboratory

  20. The connection between the radio jet and the gamma-ray emission in the radio galaxy 3C 120

    E-Print Network [OSTI]

    Casadio, Carolina; Grandi, Paola; Jorstad, Svetlana G; Marscher, Alan P; Lister, Matthew L; Kovalev, Yuri Y; Savolainen, Tuomas; Pushkarev, Alexander B

    2015-01-01T23:59:59.000Z

    We present the analysis of the radio jet evolution of the radio galaxy 3C 120 during a period of prolonged gamma-ray activity detected by the Fermi satellite between December 2012 and October 2014. We find a clear connection between the gamma-ray and radio emission, such that every period of gamma-ray activity is accompanied by the flaring of the mm-VLBI core and subsequent ejection of a new superluminal component. However, not all ejections of components are associated with gamma-ray events detectable by Fermi. Clear gamma-ray detections are obtained only when components are moving in a direction closer to our line of sight.This suggests that the observed gamma-ray emission depends not only on the interaction of moving components with the mm-VLBI core, but also on their orientation with respect to the observer. Timing of the gamma-ray detections and ejection of superluminal components locate the gamma-ray production to within almost 0.13 pc from the mm-VLBI core, which was previously estimated to lie about 0...

  1. Unveiling the nature of the unidentified gamma-ray sources VI: gamma-ray blazar candidates in the WISH survey and their radio properties

    E-Print Network [OSTI]

    Nori, M; Massaro, F; D'Abrusco, R; Paggi, A; Tosti, G; Funk, S

    2015-01-01T23:59:59.000Z

    According to the second Fermi LAT Catalog (2FGL), about one third of the gamma-ray sources listed have no assigned counterparts at lower energies. Many statistical methods have been developed to find proper counterparts for these sources. We explore the sky area covered at low radio frequency by Westerbork in the Southern Hemisphere (WISH) survey to search for blazar-like associations among the unidentified gamma-ray sources listed in the 2FGL (UGSs). Searching the WISH and NRAO VLA Sky Survey (NVSS) radio surveys within the positional uncertainty regions of the 2FGL UGSs, we select as gamma-ray blazar candidates the radio sources characterized by flat radio spectra between 352 MHz and 1400 MHz. We propose new gamma-ray blazar associations for eight UGSs and we also discuss their spectral properties at low radio frequencies. We compare the radio flux density distribution of the low radio frequency gamma-ray blazar candidates with that of gamma-ray blazars associated with other methods. We find significant dif...

  2. Hybrid model of GeV-TeV gamma ray emission from Galactic Center

    E-Print Network [OSTI]

    Yi-Qing Guo; Qiang Yuan; Cheng Liu; Ai-Feng Li

    2014-09-14T23:59:59.000Z

    The observations of high energy $\\gamma$-ray emission from the Galactic center (GC) by HESS, and recently by Fermi, suggest the cosmic ray acceleration in the GC and possibly around the supermassive black hole. In this work we propose a lepton-hadron hybrid model to explain simultaneously the GeV-TeV $\\gamma$-ray emission. Both electrons and hadronic cosmic rays were accelerated during the past activity of the GC. Then these particles would diffuse outwards and interact with the interstellar gas and background radiation field. The collisions between hadronic cosmic rays with gas is responsible to the TeV $\\gamma$-ray emission detected by HESS. With fast cooling in the strong radiation field, the electrons would cool down and radiate GeV photons through inverse Compton scattering off the soft background photons. This scenario provides a natural explanation of the observed GeV-TeV spectral shape of $\\gamma$-rays.

  3. LIMITS TO THE FRACTION OF HIGH-ENERGY PHOTON EMITTING GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Akerlof, Carl W.; Zheng, WeiKang, E-mail: akerlof@umich.edu [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109-1040 (United States)] [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109-1040 (United States)

    2013-02-20T23:59:59.000Z

    After almost four years of operation, the two instruments on board the Fermi Gamma-ray Space Telescope have shown that the number of gamma-ray bursts (GRBs) with high-energy photon emission above 100 MeV cannot exceed roughly 9% of the total number of all such events, at least at the present detection limits. In a recent paper, we found that GRBs with photons detected in the Large Area Telescope have a surprisingly broad distribution with respect to the observed event photon number. Extrapolation of our empirical fit to numbers of photons below our previous detection limit suggests that the overall rate of such low flux events could be estimated by standard image co-adding techniques. In this case, we have taken advantage of the excellent angular resolution of the Swift mission to provide accurate reference points for 79 GRB events which have eluded any previous correlations with high-energy photons. We find a small but significant signal in the co-added field. Guided by the extrapolated power-law fit previously obtained for the number distribution of GRBs with higher fluxes, the data suggest that only a small fraction of GRBs are sources of high-energy photons.

  4. Improved methods for detecting gravitational waves associated with short gamma-ray bursts

    E-Print Network [OSTI]

    A. R. Williamson; C. Biwer; S. Fairhurst; I. W. Harry; E. Macdonald; D. Macleod; V. Predoi

    2014-10-22T23:59:59.000Z

    In the era of second generation ground-based gravitational wave detectors, short gamma-ray bursts (GRBs) will be among the most promising astrophysical events for joint electromagnetic and gravitational wave observation. A targeted search for gravitational wave compact binary merger signals in coincidence with short GRBs was developed and used to analyze data from the first generation LIGO and Virgo instruments. In this paper, we present improvements to this search that enhance our ability to detect gravitational wave counterparts to short GRBs. Specifically, we introduce an improved method for estimating the gravitational wave background to obtain the event significance required to make detections; implement a method of tiling extended sky regions, as required when searching for signals associated to poorly localized GRBs from Fermi Gamma-ray Burst Monitor or the InterPlanetary Network; and incorporate astrophysical knowledge about the beaming of GRB emission to restrict the search parameter space. We describe the implementation of these enhancements and demonstrate how they improve the ability to observe binary merger gravitational wave signals associated with short GRBs.

  5. Gamma Ray Burst Central Engines

    E-Print Network [OSTI]

    Todd A. Thompson

    2008-07-04T23:59:59.000Z

    I review aspects of the theory of long-duration gamma-ray burst (GRB) central engines. I focus on the requirements of any model; these include the angular momentum of the progenitor, the power, Lorentz factor, asymmetry, and duration of the flow, and both the association and the non-association with bright supernovae. I compare and contrast the collapsar and millisecond proto-magnetar models in light of these requirements. The ability of the latter model to produce a flow with Lorentz factor ~100 while simultaneously maintaining a kinetic luminosity of ~10^50 ergs/s for a timescale of ~10-100 s is emphasized.

  6. Black Stars and Gamma Ray Bursts

    E-Print Network [OSTI]

    Tanmay Vachaspati

    2007-06-08T23:59:59.000Z

    Stars that are collapsing toward forming a black hole but are frozen near the Schwarzschild horizon are termed ``black stars''. Collisions of black stars, in contrast to black hole collisions, may be sources of gamma ray bursts, whose basic parameters are estimated quite simply and are found to be consistent with observed gamma ray bursts. Black star gamma ray bursts should be preceded by gravitational wave emission similar to that from the coalescence of black holes.

  7. Evidence of cross-correlation between the CMB lensing and the gamma-ray sky

    E-Print Network [OSTI]

    N. Fornengo; L. Perotto; M. Regis; S. Camera

    2015-03-02T23:59:59.000Z

    We report the measurement of the angular power spectrum of cross-correlation between the unresolved component of the Fermi-LAT gamma-ray sky-maps and the CMB lensing potential map reconstructed by the Planck satellite. The matter distribution in the Universe determines the bending of light coming from the last scattering surface. At the same time, the matter density drives the growth history of astrophysical objects, including their capability at generating non-thermal phenomena, which in turn give rise to gamma-ray emissions. The Planck lensing map provides information on the integrated distribution of matter, while the integrated history of gamma-ray emitters is imprinted in the Fermi-LAT sky maps. We report here the first evidence of their correlation. We find that the multipole dependence of the cross-correlation measurement is in agreement with current models of the gamma-ray luminosity function for AGN and star forming galaxies, with a statistical evidence of 3.0$\\sigma$. Moreover, its amplitude can in general be matched only assuming that these extra-galactic emitters are also the bulk contribution of the measured isotopic gamma-ray background (IGRB) intensity. This leaves little room for a big contribution from galactic sources to the IGRB measured by Fermi-LAT, pointing toward a direct evidence of the extragalactic origin of the IGRB.

  8. Gravitational Waves versus X and Gamma Ray Emission in a Short Gamma-Ray Burst

    E-Print Network [OSTI]

    F. G. Oliveira; Jorge A. Rueda; Remo Ruffini

    2014-03-28T23:59:59.000Z

    The recent progress in the understanding the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst, GRB 090227B, allows to give an estimate of the gravitational waves versus the X and Gamma-ray emission in a short gamma-ray burst.

  9. The first gamma-ray detection of the narrow-line Seyfert 1 FBQS J1644+2619

    E-Print Network [OSTI]

    D'Ammando, F; Larsson, J; Giroletti, M

    2015-01-01T23:59:59.000Z

    We report the discovery of gamma-ray emission from the narrow-line Seyfert 1 (NLSy1) galaxy FBQS J1644+2619 by the Large Area Telescope on board the Fermi satellite. The Third Fermi LAT Source catalogue reports an unidentified gamma-ray source, detected over the first four years of Fermi operation, 0.23 deg from the radio position of the NLSy1. Analysing 76 months of gamma-ray data (2008 August 4-2014 December 31) we are able to better constrain the localization of the gamma-ray source. The new position of the gamma-ray source is 0.05 deg from FBQS J1644+2619, suggesting a spatial association with the NLSy1. This is the sixth NLSy1 detected at high significance by Fermi-LAT so far. Notably, a significant increase of activity was observed in gamma-rays from FBQS J1644+2619 during 2012 July-October, and an increase of activity in V-band was detected by the Catalina Real-Time Sky Survey in the same period.

  10. GeV Emission from Collisional Magnetized Gamma Ray Bursts

    E-Print Network [OSTI]

    P. Mészáros; M. J. Rees

    2011-04-26T23:59:59.000Z

    Magnetic fields may play a dominant role in gamma-ray bursts, and recent observations by the Fermi satellite indicate that GeV radiation, when detected, arrives delayed by seconds from the onset of the MeV component. Motivated by this, we discuss a magnetically dominated jet model where both magnetic dissipation and nuclear collisions are important. We show that, for parameters typical of the observed bursts, such a model involving a realistic jet structure can reproduce the general features of the MeV and a separate GeV radiation component, including the time delay between the two. The model also predicts a multi-GeV neutrino component.

  11. Galactic Center Gamma Ray Excess and Higgs Boson(s)

    E-Print Network [OSTI]

    Ipek, Seyda

    2015-01-01T23:59:59.000Z

    There is evidence for an excess of gamma rays with $O({\\rm GeV})$ energy coming from the Galactic Center in data from the Fermi Telescope. The spectrum of the excess is well fit by 30 GeV dark matter annihilating into a pair of $b$ quarks with a cross section expected from a thermal relic. For an explanation of this excess, we study a renormalizable model where dark matter couples to the SM via a pseudoscalar that mixes with the $CP$-odd Higgs boson of a Two HIggs Doublet Model. We report the constraints on this model from direct detection, Higgs decays, and rare $B$ meson decays.

  12. VERITAS OBSERVATIONS OF GAMMA-RAY BURSTS DETECTED BY SWIFT

    SciTech Connect (OSTI)

    Acciari, V. A.; Benbow, W. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Aliu, E.; Errando, M. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Arlen, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Aune, T. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Beilicke, M.; Buckley, J. H.; Bugaev, V. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Bradbury, S. M. [School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT (United Kingdom); Byrum, K. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Cannon, A.; Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Cesarini, A.; Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Christiansen, J. L. [Physics Department, California Polytechnic State University, San Luis Obispo, CA 94307 (United States); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Cui, W. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Duke, C. [Department of Physics, Grinnell College, Grinnell, IA 50112-1690 (United States); Falcone, A. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); and others

    2011-12-10T23:59:59.000Z

    We present the results of 16 Swift-triggered Gamma-ray burst (GRB) follow-up observations taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) telescope array from 2007 January to 2009 June. The median energy threshold and response time of these observations were 260 GeV and 320 s, respectively. Observations had an average duration of 90 minutes. Each burst is analyzed independently in two modes: over the whole duration of the observations and again over a shorter timescale determined by the maximum VERITAS sensitivity to a burst with a t{sup -1.5} time profile. This temporal model is characteristic of GRB afterglows with high-energy, long-lived emission that have been detected by the Large Area Telescope on board the Fermi satellite. No significant very high energy (VHE) gamma-ray emission was detected and upper limits above the VERITAS threshold energy are calculated. The VERITAS upper limits are corrected for gamma-ray extinction by the extragalactic background light and interpreted in the context of the keV emission detected by Swift. For some bursts the VHE emission must have less power than the keV emission, placing constraints on inverse Compton models of VHE emission.

  13. CONSTRAINTS ON VERY HIGH ENERGY GAMMA-RAY EMISSION FROM GAMMA-RAY BURSTS R. Atkins,1,2

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    CONSTRAINTS ON VERY HIGH ENERGY GAMMA-RAY EMISSION FROM GAMMA-RAY BURSTS R. Atkins,1,2 W. Benbow,3 emission from gamma-ray bursts (GRBs) during the prompt emission phase. Detection of >100 GeV counterparts on potential GRB models. Subject headinggs: gamma rays: bursts -- gamma rays: observations 1. INTRODUCTION

  14. Observations of Gamma-Ray Bursts at Extreme Energies

    E-Print Network [OSTI]

    Aune, Taylor

    2012-01-01T23:59:59.000Z

    of Gamma-Ray Bursts . . . . . . . . . . . . . Redshift-CRUZ OBSERVATIONS OF GAMMA-RAY BURSTS AT EXTREME ENERGIES ADedication xix Acknowledgments xx 1 Gamma-Ray Bursts 1.1

  15. A history of gamma ray bursts and other astronomical conundrums

    E-Print Network [OSTI]

    Trimble, V

    2006-01-01T23:59:59.000Z

    V. Trimble, in “Gamma Ray Bursts: 30 Years of Discovery,”V. Trimble, in “Gamma Ray Bursts,” Ed. C. Ho et al. ,A History of Gamma Ray Bursts and Other Astronomical

  16. Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1

    E-Print Network [OSTI]

    ,

    2011-01-01T23:59:59.000Z

    We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) onboard the \\emph{Fermi} Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV--100 GeV can be described by a broken power-law function with a break of 2.4 $\\pm$ 0.6 (stat) $\\pm$ 1.2 (sys) GeV, and photon indices of 2.10 $\\pm$ 0.06 (stat) $\\pm$ 0.10 (sys) below the break and 2.70 $\\pm$ 0.12 (stat) $\\pm$ 0.14...

  17. The soft gamma-ray pulsar population: an high-energy overview

    E-Print Network [OSTI]

    Kuiper, L

    2015-01-01T23:59:59.000Z

    At high-energy gamma-rays (>100 MeV) the Large Area Telescope (LAT) on the Fermi satellite already detected more than 145 rotation-powered pulsars (RPPs), while the number of pulsars seen at soft gamma-rays (20 keV - 30 MeV) remained small. We present a catalogue of 18 non-recycled RPPs from which presently non-thermal pulsed emission has been securely detected at soft gamma-rays above 20 keV, and characterize their pulse profiles and energy spectra. For 14 of them we report new results, (re)analysing mainly data from RXTE, INTEGRAL, XMM-Newton and Chandra. The soft gamma-pulsars are all fast rotators and on average ~9.3x younger and ~ 43x more energetic than the Fermi LAT sample. The majority (11 members) exhibits broad, structured single pulse profiles, and only 6 have double (or even multiple, Vela) pulses. Fifteen soft gamma-ray pulsar show hard power-law spectra in the hard X-ray band and reach maximum luminosities typically in the MeV range. For only 7 of the 18 soft gamma-ray pulsars pulsed emission ha...

  18. Comment on "A limit on the variation of the speed of light arising from quantum gravity effects" aka "Testing Einstein's special relativity with Fermi's short hard gamma-ray burst GRB090510"

    E-Print Network [OSTI]

    Konstantin G. Zloshchastiev

    2009-11-30T23:59:59.000Z

    Recently the Fermi GBM and LAT Collaborations reported their new observational data disfavoring quite a number of the quantum gravity theories, including the one suggesting the nonlinear (logarithmic) modification of a quantum wave equation. We show that the latter is still far from being ruled out: it is not only able to explain the new data but also its phenomenological implications turn out to be more vast (and more interesting) than one expected before.

  19. FERMI-LAT OBSERVATIONS OF SUPERNOVA REMNANTS INTERACTING WITH MOLECULAR CLOUDS: W41, MSH 17-39, AND G337.7-0.1

    E-Print Network [OSTI]

    Castro, Daniel

    We report the detection of ?-ray emission coincident with three supernova remnants (SNRs) using data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. W41, G337.7-0.1, and MSH 17-39 are SNRs known ...

  20. Gamma-Ray Bursts and Particle Astrophysics

    E-Print Network [OSTI]

    B. Gendre

    2008-07-24T23:59:59.000Z

    Gamma-ray bursts are violent events occurring randomly in the sky. In this review, I will present the fireball model, proposed to explain the phenomenon of gamma-ray bursts. This model has important consequences for the production and observation at Earth of gravitational waves, high energy neutrinos, cosmic rays and high energy photons, and the second part of this review will be focused on these aspects. A last section will briefly discuss the topic of the use of gamma-ray bursts as standard candles and possible cosmological studies.

  1. Cosmic Ray e +/(e- + e+), p-bar/p Ratios Explained by an Injection Model Based on 2 Gamma-ray Observations

    SciTech Connect (OSTI)

    Kamae, T.; /KIPAC, Menlo Park /SLAC; Lee, S.-H.; /KIPAC, Menlo Park; Baldini, L.; /INFN, Pisa; Giordano, F.; /Bari Polytechnic /INFN, Bari; Grondin, M.-H.; /Bordeaux U.; Latronico, L.; /INFN, Pisa; Lemoine-Goumard, M.; /Bordeaux U.; Sgro, C.; /INFN, Pisa; Tanaka, T.; Uchiyama, Y.; /KIPAC, Menlo Park

    2010-12-16T23:59:59.000Z

    We present a model of cosmic ray (CR) injection into the Galactic space based on recent {gamma}-ray observations of supernova remnants (SNRs) and pulsar wind nebulae (PWNe) by the Fermi Large Area Telescope (Fermi) and atmospheric Cherenkov telescopes (ACTs). Steady-state (SS) injection of nuclear particles and electrons (e{sup -}) from the Galactic ensemble of SNRs, and electrons and positrons (e{sup +}) from the Galactic ensemble of PWNe are assumed, with their spectra deduced from {gamma}-ray observations and recent evolution models. The ensembles of SNRs and PWNe are assumed to share the same spatial distributions and the secondary CR production in dense molecular clouds interacting with SNRs is incorporated in the model. Propagation of CRs to Earth is calculated using GALPROP with 2 source distributions and 2 Galaxy halo sizes. We show that this observation-based model reproduces the positron fraction e{sup +}/(e{sup -} + e{sup +}) and antiproton-to-proton ratio ({bar p}/p) reported by PAMELA reasonably well without calling for new sources. Significant discrepancy is found, however, between our model and the e{sup -} + e{sup +} spectrum measured by Fermi below {approx} 20 GeV. Important quantities for Galactic CRs, including their energy injection, average lifetime, and mean gas density along their typical propagation path are also presented.

  2. Young Pulsars and the Galactic Center GeV Gamma-ray Excess

    E-Print Network [OSTI]

    O'Leary, Ryan M; Kerr, Matthew; Dexter, Jason

    2015-01-01T23:59:59.000Z

    Studies of Fermi data indicate an excess of GeV gamma rays around the Galactic center (GC), possibly due to dark matter. We show that young gamma-ray pulsars can yield a similar signal. First, a high concentration of GC supernovae naturally leads to a population of kicked pulsars symmetric about the GC. Second, while very-young pulsars with soft spectra reside near the Galactic plane, pulsars with spectra that have hardened with age accumulate at larger angles. This combination, including unresolved foreground pulsars, traces the morphology and spectrum of the Excess.

  3. Young Pulsars and the Galactic Center GeV Gamma-ray Excess

    E-Print Network [OSTI]

    Ryan M. O'Leary; Matthew D. Kistler; Matthew Kerr; Jason Dexter

    2015-04-09T23:59:59.000Z

    Studies of Fermi data indicate an excess of GeV gamma rays around the Galactic center (GC), possibly due to dark matter. We show that young gamma-ray pulsars can yield a similar signal. First, a high concentration of GC supernovae naturally leads to a population of kicked pulsars symmetric about the GC. Second, while very-young pulsars with soft spectra reside near the Galactic plane, pulsars with spectra that have hardened with age accumulate at larger angles. This combination, including unresolved foreground pulsars, traces the morphology and spectrum of the Excess.

  4. Gamma-ray Burst Cosmology

    E-Print Network [OSTI]

    Wang, F Y; Liang, E W

    2015-01-01T23:59:59.000Z

    Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the largest distances yet explored in the Universe. GRBs, as bright beacons in the deep Universe, would be the ideal tool to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal enrichment history of the Universe. In this article, we review the luminosity correlations of GRBs, and implications for constraining the cosmological parameters and dark energy. Observations show that the progenitors of long GRBs are massive stars. So it is expected that long GRBs are tracers of star formation rate. We also review the high-redshift star formation rate derived from GRBs, and implications for the cosmic reionization history. The afterglows of GRBs generally have broken power-law spectra, so it...

  5. Energetics of Gamma Ray Bursts

    E-Print Network [OSTI]

    Raul Jimenez; David Band; Tsvi Piran

    2001-03-16T23:59:59.000Z

    We determine the distribution of total energy emitted by gamma-ray bursts for bursts with fluences and distance information. Our core sample consists of eight bursts with BATSE spectra and spectroscopic redshifts. We extend this sample by adding four bursts with BATSE spectra and host galaxy R magnitudes. From these R magnitudes we calculate a redshift probability distribution; this method requires a model of the host galaxy population. From a sample of ten bursts with both spectroscopic redshifts and host galaxy R magnitudes (some do not have BATSE spectra) we find that the burst rate is proportional to the galaxy luminosity at the epoch of the burst. Assuming that the total energy emitted has a log-normal distribution, we find that the average emitted energy (assumed to be radiated isotropically) is $gamma iso} > = 1.3^{+1.2}_{-1.0} \\times 10^{53}$ ergs (for H$_0$ = 65 km s$^{-1}$ Mpc$^{-1}$, $\\Omega_m=0.3$ and $\\Omega_\\Lambda=0.7$); the distribution has a logarithmic width of $\\sigma_\\gamma=1.7^{+0.7}_{-0.3}$. The corresponding distribution of X-ray afterglow energy (for seven bursts) has $ = 4.0^{+1.6}_{-1.8} \\times 10^{51}$ergs and $\\sigma_X = 1.3^{+0.4}_{-0.3}$. For completeness, we also provide spectral fits for all bursts with BATSE spectra for which there were afterglow searches.

  6. Common Origin of 3.55 keV X-Ray Line and Galactic Center Gamma Ray Excess in a Radiative Neutrino Mass Model

    E-Print Network [OSTI]

    Borah, Debasish; Adhikari, Rathin

    2015-01-01T23:59:59.000Z

    We attempt to simultaneously explain the recently observed 3.55 keV X-ray line in the analysis of XMM-Newton telescope data and the galactic center gamma ray excess observed by the Fermi gamma ray space telescope within an abelian gauge extension of standard model. We consider a two component dark matter scenario with a mass difference 3.55 keV such that the heavier one can decay into the lighter one and a photon with energy 3.55 keV. The lighter dark matter candidate is protected from decaying into the standard model particles by a remnant $Z_2$ symmetry into which the abelian gauge symmetry gets spontaneously broken. If the mass of the dark matter particle is chosen to be within $31-40$ GeV, then this model can also explain the galactic center gamma ray excess if the dark matter annihilation into $b\\bar{b}$ pairs has a cross section of $\\langle \\sigma v \\rangle \\simeq (1.4-2.0) \\times 10^{-26} \\; \\text{cm}^3/\\text{s}$. We constrain the model from the requirement of producing correct dark matter relic densit...

  7. Gravitational waves and gamma-ray bursts

    E-Print Network [OSTI]

    Alessandra Corsi; for the LIGO Scientific Collaboration; for the Virgo Collaboration

    2012-05-11T23:59:59.000Z

    Gamma-Ray Bursts are likely associated with a catastrophic energy release in stellar mass objects. Electromagnetic observations provide important, but indirect information on the progenitor. On the other hand, gravitational waves emitted from the central source, carry direct information on its nature. In this context, I give an overview of the multi-messenger study of gamma-ray bursts that can be carried out by using electromagnetic and gravitational wave observations. I also underline the importance of joint electromagnetic and gravitational wave searches, in the absence of a gamma-ray trigger. Finally, I discuss how multi-messenger observations may probe alternative gamma-ray burst progenitor models, such as the magnetar scenario.

  8. Studying Gamma Ray Bursts from a

    E-Print Network [OSTI]

    ?umer, Slobodan

    Studying Gamma Ray Bursts from a new perspective! {... Unraveling some mysteries and adding new Radio Op0cal X-ray Short ( energy -ray photons... ... accompained by a considerable long las0ng emission

  9. Can gamma-ray bursts constrain quintessence?

    E-Print Network [OSTI]

    T. Di Girolamo; R. Catena; M. Vietri; G. Di Sciascio

    2005-04-27T23:59:59.000Z

    Using the narrow clustering of the geometrically corrected gamma-ray energies released by gamma-ray bursts, we investigate the possibility of using these sources as standard candles to probe cosmological parameters such as the matter density Omega_m and the cosmological constant energy density Omega_Lambda. By simulating different samples of gamma-ray bursts, we find that Omega_m can be determined with accuracy ~7% with data from 300 sources. We also show that, if Omega = 1 is due to a quintessence field, some of the models proposed in the literature may be discriminated from a Universe with cosmological constant, by a similar-sized sample of gamma-ray bursts.

  10. Thermal neutron capture gamma-rays

    SciTech Connect (OSTI)

    Tuli, J.K.

    1983-01-01T23:59:59.000Z

    The energy and intensity of gamma rays as seen in thermal neutron capture are presented. Only those (n,..cap alpha..), E = thermal, reactions for which the residual nucleus mass number is greater than or equal to 45 are included. These correspond to evaluations published in Nuclear Data Sheets. The publication source data are contained in the Evaluated Nuclear Structure Data File (ENSDF). The data presented here do not involve any additional evaluation. Appendix I lists all the residual nuclides for which the data are included here. Appendix II gives a cumulated index to A-chain evaluations including the year of publication. The capture gamma ray data are given in two tables - the Table 1 is the list of all gamma rays seen in (n,..gamma..) reaction given in the order of increasing energy; the Table II lists the gamma rays according to the nuclide.

  11. Mining Gamma-Ray Burst Data

    E-Print Network [OSTI]

    Jon Hakkila; Richard J. Roiger; David J. Haglin; Robert S. Mallozzi; Geoffrey N. Pendleton; Charles A. Meegan

    2000-11-30T23:59:59.000Z

    Gamma-ray bursts provide what is probably one of the messiest of all astrophysical data sets. Burst class properties are indistinct, as overlapping characteristics of individual bursts are convolved with effects of instrumental and sampling biases. Despite these complexities, data mining techniques have allowed new insights to be made about gamma-ray burst data. We demonstrate how data mining techniques have simultaneously allowed us to learn about gamma-ray burst detectors and data collection, cosmological effects in burst data, and properties of burst subclasses. We discuss the exciting future of this field, and the web-based tool we are developing (with support from the NASA AISR Program). We invite others to join us in AI-guided gamma-ray burst classification (http://grb.mnsu.edu/grb/).

  12. A correlation between hard gamma-ray sources and cosmic voids along the line of sight

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Furniss, A.; Sutter, P. M.; Primack, J. R.; Dominguez, A.

    2014-11-25T23:59:59.000Z

    We estimate the galaxy density along lines of sight to hard extragalactic gamma-ray sources by correlating source positions on the sky with a void catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray sources that are detected at very high energy (VHE; E > 100 GeV) or have been highlighted as VHE-emitting candidates in the Fermi Large Area Telescope hard source catalog (together referred to as “VHE-like” sources) are distributed along underdense lines of sight at the 2.4#27; level. There is also a less suggestive correlation for the Fermi hard source population (1.7#27;). A correlation between 10-500 GeV flux and underdense fraction along the line of sight for VHE-like and Fermi hard sources is found at 2.4#27; and 2.6#27;, calculated from the Pearson correlation coefficients of r = 0.57 and 0.47, respectively. The preference for underdense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. We investigate whether this marginal correlation might be a result of lower extragalactic background light (EBL) photon density within the underdense regions and find that, even in the most extreme case of a entirely underdense sight line, the EBL photon density is only 2% less than the nominal EBL density. Translating this into gamma-ray attenuation along the line of sight for a highly attenuated source with opacity #28;(E, z) #24; 5, we estimate that the attentuation of gamma-rays decreases no more than 10%. This decrease, although non-neglible, is unable to account for the apparent hard source correlation with underdense lines of sight.

  13. A correlation between hard gamma-ray sources and cosmic voids along the line of sight

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Furniss, A.; Sutter, P. M.; Primack, J. R.; Dominguez, A.

    2014-11-25T23:59:59.000Z

    We estimate the galaxy density along lines of sight to hard extragalactic gamma-ray sources by correlating source positions on the sky with a void catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray sources that are detected at very high energy (VHE; E > 100 GeV) or have been highlighted as VHE-emitting candidates in the Fermi Large Area Telescope hard source catalog (together referred to as “VHE-like” sources) are distributed along underdense lines of sight at the 2.4#27; level. There is also a less suggestive correlation for the Fermi hard source population (1.7#27;). A correlation between 10-500 GeVmore »flux and underdense fraction along the line of sight for VHE-like and Fermi hard sources is found at 2.4#27; and 2.6#27;, calculated from the Pearson correlation coefficients of r = 0.57 and 0.47, respectively. The preference for underdense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. We investigate whether this marginal correlation might be a result of lower extragalactic background light (EBL) photon density within the underdense regions and find that, even in the most extreme case of a entirely underdense sight line, the EBL photon density is only 2% less than the nominal EBL density. Translating this into gamma-ray attenuation along the line of sight for a highly attenuated source with opacity #28;(E, z) #24; 5, we estimate that the attentuation of gamma-rays decreases no more than 10%. This decrease, although non-neglible, is unable to account for the apparent hard source correlation with underdense lines of sight.« less

  14. Gamma Ray Bursts from Ordinary Cosmic Strings

    E-Print Network [OSTI]

    R. H. Brandenberger; A. T. Sornborger; M. Trodden

    1993-02-12T23:59:59.000Z

    We give an upper estimate for the number of gamma ray bursts from ordinary (non-superconducting) cosmic strings expected to be observed at terrestrial detectors. Assuming that cusp annihilation is the mechanism responsible for the bursts we consider strings arising at a GUT phase transition and compare our estimate with the recent BATSE results. Further we give a lower limit for the effective area of future detectors designed to detect the cosmic string induced flux of gamma ray bursts.

  15. The HAWC Gamma-Ray Observatory: Sensitivity to Steady and Transient Sources of Gamma Rays

    E-Print Network [OSTI]

    Abeysekara, A U; Alvarez, C; Álvarez, J D; Arceo, R; Arteaga-Velázquez, J C; Solares, H A Ayala; Barber, A S; Baughman, B M; Bautista-Elivar, N; Belmont, E; BenZvi, S Y; Berley, D; Rosales, M Bonilla; Braun, J; Caballero-Lopez, R A; Caballero-Mora, K S; Carramińana, A; Castillo, M; Cotti, U; Cotzomi, J; de la Fuente, E; De León, C; DeYoung, T; Hernandez, R Diaz; Díaz-Vélez, J C; Dingus, B L; DuVernois, M A; Ellsworth, R W; Fernandez, A; Fiorino, D W; Fraija, N; Galindo, A; Garfias, F; González, L X; González, M M; Goodman, J A; Grabski, V; Gussert, M; Hampel-Arias, Z; Hui, C M; Hüntemeyer, P; Imran, A; Iriarte, A; Karn, P; Kieda, D; Kunde, G J; Lara, A; Lauer, R J; Lee, W H; Lennarz, D; Vargas, H León; Linares, E C; Linnemann, J T; Longo, M; Luna-GarcIa, R; Marinelli, A; Martinez, H; Martinez, O; Martínez-Castro, J; Matthews, J A J; Miranda-Romagnoli, P; Moreno, E; Mostafá, M; Nava, J; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T; Patricelli, B; Pelayo, R; Pérez-Pérez, E G; Pretz, J; Rivičre, C; Rosa-González, D; Salazar, H; Salesa, F; Sanchez, F E; Sandoval, A; Santos, E; Schneider, M; Silich, S; Sinnis, G; Smith, A J; Sparks, K; Springer, R W; Taboada, I; Toale, P A; Tollefson, K; Torres, I; Ukwatta, T N; Villaseńor, L; Weisgarber, T; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Younk, P W; Zaborov, D; Zepeda, A; Zhou, H

    2013-01-01T23:59:59.000Z

    The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is designed to record air showers produced by cosmic rays and gamma rays between 100 GeV and 100 TeV. Because of its large field of view and high livetime, HAWC is well-suited to measure gamma rays from extended sources, diffuse emission, and transient sources. We describe the sensitivity of HAWC to emission from the extended Cygnus region as well as other types of galactic diffuse emission; searches for flares from gamma-ray bursts and active galactic nuclei; and the first measurement of the Crab Nebula with HAWC-30.

  16. Results from the Milagro Gamma-Ray Observatory

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    V energies, and a search for transient emission above 100 GeV from gamma-ray bursts. 1 Introduction remnants and gamma-ray bursts (GRB). Gamma rays are also produced when high-energy cosmic rays interactResults from the Milagro Gamma-Ray Observatory E. Blaufuss for the Milagro Collaboration a,1 , a

  17. GeV Gamma-ray Flux Upper Limits from Clusters of Galaxies

    E-Print Network [OSTI]

    al., M Ackermann et

    2010-01-01T23:59:59.000Z

    The detection of diffuse radio emission associated with clusters of galaxies indicates populations of relativistic leptons infusing the intracluster medium. Those electrons and positrons are either injected into and accelerated directly in the intracluster medium, or produced as secondary pairs by cosmic-ray ions scattering on ambient protons. Radiation mechanisms involving the energetic leptons together with decay of neutral pions produced by hadronic interactions have the potential to produce abundant GeV photons. Here, we report on the search for GeV emission from clusters of galaxies using data collected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi) from August 2008 to February 2010. Thirty-three galaxy clusters have been selected according to their proximity and high mass, X-ray flux and temperature, and indications of non-thermal activity for this study. We report upper limits on the photon flux in the range 0.2-100 GeV towards a sample of observed clusters (typical va...

  18. Do Gamma-Ray Bursts Come from the Oort Cloud?

    E-Print Network [OSTI]

    T. E. Clarke; O. Blaes; adn S. Tremaine

    1993-10-02T23:59:59.000Z

    We examine the possibility that gamma-ray bursts arise from sources in the Oort comet cloud, basing most of our arguments on accepted models for the formation and spatial distribution of the cloud. We identify three severe problems with such models: (1) There is no known mechanism for producing bursts that can explain the observed burst rate and energetics without violating other observational constraints. (2) The bright source counts cannot be reconciled with standard models for the phase-space distribution of objects in the Oort cloud. (3) The observed isotropy of the available burst data is inconsistent with the expected angular distribution of sources in the Oort cloud. We therefore assert that Oort cloud models of gamma-ray bursts are extremely implausible.

  19. Constraining the extension of a possible gamma-ray halo of 3C 279 from 2008-2014 solar occultations

    E-Print Network [OSTI]

    Kotelnikov, Egor; Troitsky, Sergey

    2014-01-01T23:59:59.000Z

    The angular extension of the gamma-ray image of 3C 279 may be constrained by studying its solar occultations as suggested by Fairbairn et al. (2010). We perform this kind of analysis for seven occultations observed by Fermi-LAT in 2008-2014, using the Fermi-LAT Solar System tools. The results are interpreted in terms of models with extended gamma-ray halo of 3C 279; first constraints on the size and the flux of the halo are reported.

  20. Fermi Large Area Telescope Observations of the Cosmic-Ray Induced

    SciTech Connect (OSTI)

    Abdo, A.

    2012-02-29T23:59:59.000Z

    We report on measurements of the cosmic-ray induced {gamma}-ray emission of Earth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The LAT has observed the Earth during its commissioning phase and with a dedicated Earth-limb following observation in September 2008. These measurements yielded {approx} 6.4 x 10{sup 6} photons with energies > 100 MeV and {approx} 250 hours total livetime for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission - often referred to as Earth albedo gamma-ray emission - has a power-law shape up to 500 GeV with spectral index {Lambda} = 2.79 {+-} 0.06.

  1. DETECTION OF THE COSMIC {gamma}-RAY HORIZON FROM MULTIWAVELENGTH OBSERVATIONS OF BLAZARS

    SciTech Connect (OSTI)

    Dominguez, A.; Siana, B. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Finke, J. D. [U.S. Naval Research Laboratory, Space Science Division, Code 7653, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Prada, F. [Campus of International Excellence UAM-CSIC, Cantoblanco, E-28049 Madrid (Spain); Primack, J. R. [Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Kitaura, F. S. [Leibniz-Institut fuer Astrophysik (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Paneque, D., E-mail: albertod@ucr.edu [Kavli Institute for Particle Astrophysics and Cosmology, SLAC, Stanford University, Stanford, CA 94305 (United States)

    2013-06-10T23:59:59.000Z

    The first statistically significant detection of the cosmic {gamma}-ray horizon (CGRH) that is independent of any extragalactic background light (EBL) model is presented. The CGRH is a fundamental quantity in cosmology. It gives an estimate of the opacity of the universe to very high energy (VHE) {gamma}-ray photons due to photon-photon pair production with the EBL. The only estimations of the CGRH to date are predictions from EBL models and lower limits from {gamma}-ray observations of cosmological blazars and {gamma}-ray bursts. Here, we present homogeneous synchrotron/synchrotron self-Compton (SSC) models of the spectral energy distributions of 15 blazars based on (almost) simultaneous observations from radio up to the highest energy {gamma}-rays taken with the Fermi satellite. These synchrotron/SSC models predict the unattenuated VHE fluxes, which are compared with the observations by imaging atmospheric Cherenkov telescopes. This comparison provides an estimate of the optical depth of the EBL, which allows us a derivation of the CGRH through a maximum likelihood analysis that is EBL-model independent. We find that the observed CGRH is compatible with the current knowledge of the EBL.

  2. Unveiling the population of orphan Gamma Ray Bursts

    E-Print Network [OSTI]

    Ghirlanda, G; Campana, S; Vergani, S D; Japelj, J; Bernardini, M G; Burlon, D; D'Avanzo, P; Melandri, A; Gomboc, A; Nappo, F; Paladini, R; Pescalli, A; Salafia, O S; Tagliaferri, G

    2015-01-01T23:59:59.000Z

    Gamma Ray Bursts are detectable in the gamma-ray band if their jets are oriented towards the observer. However, for each GRB with a typical theta_jet, there should be ~2/theta_jet^2 bursts whose emission cone is oriented elsewhere in space. These off-axis bursts can be eventually detected when, due to the deceleration of their relativistic jets, the beaming angle becomes comparable to the viewing angle. Orphan Afterglows (OA) should outnumber the current population of bursts detected in the gamma-ray band even if they have not been conclusively observed so far at any frequency. We compute the expected flux of the population of orphan afterglows in the mm, optical and X-ray bands through a population synthesis code of GRBs and the standard afterglow emission model. We estimate the detection rate of OA by on-going and forthcoming surveys. The average duration of OA as transients above a given limiting flux is derived and described with analytical expressions: in general OA should appear as daily transients in o...

  3. Accessing the population of high redshift Gamma Ray Bursts

    E-Print Network [OSTI]

    Ghirlanda, G; Ghisellini, G; Mereghetti, S; Tagliaferri, G; Campana, S; Osborne, J P; O'Brien, P; Tanvir, N; Willingale, R; Amati, L; Basa, S; Bernardini, M G; Burlon, D; Covino, S; D'Avanzo, P; Frontera, F; Gotz, D; Melandri, A; Nava, L; Piro, L; Vergani, S D

    2015-01-01T23:59:59.000Z

    Gamma Ray Bursts (GRBs) are a powerful probe of the high redshift Universe. We present a tool to estimate the detection rate of high-z GRBs by a generic detector with defined energy band and sensitivity. We base this on a population model that reproduces the observed properties of GRBs detected by Swift, Fermi and CGRO in the hard X-ray and gamma-ray bands. We provide the expected cumulative distributions of the flux and fluence of simulated GRBs in different energy bands. We show that scintillator detectors, operating at relatively high energies (e.g. tens of keV to the MeV), can detect only the most luminous GRBs at high redshifts due to the link between the peak spectral energy and the luminosity (Ep-Liso) of GRBs. We show that the best strategy for catching the largest number of high-z bursts is to go softer (e.g. in the soft X-ray band) but with a very high sensitivity. For instance, an imaging soft X-ray detector operating in the 0.2-5 keV energy band reaching a sensitivity, corresponding to a fluence o...

  4. Observations of the Isotropic Diffuse Gamma-ray Background with the EGRET Telescope

    E-Print Network [OSTI]

    T. D. Willis

    2002-01-30T23:59:59.000Z

    An Isotropic Diffuse Gamma-Ray Background (IDGRB) in the spectral range 30-10,000 MeV was first reported in the early 1970's using measurements made by the SAS-2 instrument. Data recorded by the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory (CGRO) over the last 4 years are analysed in order to extract the best measurement yet made of the IDGRB. Extensive analysis of the EGRET instrumental background is presented in order to demonstrate that an uncontaminated data set can be extracted from the EGRET data. A model of the high latitude galactic diffuse foreground emission is presented and the existence of an IDGRB is confirmed. Spatial and spectral analysis of this background is presented. In addition, point source analysis at high galactic latitudes is performed to reveal the existence of a population of extragalactic sources. The characteristics of this population are examined and models of its flux distribution are reported. The question of whether the IDGRB is composed of unresolved point sources is addressed using fluctuation analysis. Finally, possible future directions for gamma ray astronomy are examined through simulations of a future gamma ray telescope: the Gamma-ray Large Area Space Telescope (GLAST). The GLAST baseline design is described and its scientific performance is evaluated. The ability of this telescope to detect 1,000-10,000 new extragalactic sources is demonstrated and the likely impact on the study of the IDGRB is considered.

  5. A supersymmetric model of gamma ray bursts

    E-Print Network [OSTI]

    L. Clavelli; G. Karatheodoris

    2005-08-08T23:59:59.000Z

    We propose a model for gamma ray bursts in which a star subject to a high level of fermion degeneracy undergoes a phase transition to a supersymmetric state. The burst is initiated by the transition of fermion pairs to sfermion pairs which, uninhibited by the Pauli exclusion principle, can drop to the ground state of minimum momentum through photon emission. The jet structure is attributed to the Bose statistics of sfermions whereby subsequent sfermion pairs are preferentially emitted into the same state (sfermion amplification by stimulated emission). Bremsstrahlung gamma rays tend to preserve the directional information of the sfermion momenta and are themselves enhanced by stimulated emission.

  6. Redshift indicators for gamma-ray bursts

    E-Print Network [OSTI]

    J-L. Atteia

    2005-05-04T23:59:59.000Z

    The measure of the distances and luminosities of gamma-ray bursts (GRBs) led to the discovery that many GRB properties are strongly correlated with their intrinsic luminosity, leading to the construction of reliable luminosity indicators. These GRB luminosity indicators have quickly found applications, like the construction of 'pseudo-redshifts', or the measure of luminosity distances, which can be computed independently of the measure of the redshift. In this contribution I discuss various issues connected with the construction of luminosity-redshift indicators for gamma-ray bursts.

  7. Gamma-Ray Bursts: Jets and Energetics

    E-Print Network [OSTI]

    D. A. Frail

    2003-11-12T23:59:59.000Z

    The relativistic outflows from gamma-ray bursts are now thought to be narrowly collimated into jets. After correcting for this jet geometry there is a remarkable constancy of both the energy radiated by the burst and the kinetic energy carried by the outflow. Gamma-ray bursts are still the most luminous explosions in the Universe, but they release energies that are comparable to supernovae. The diversity of cosmic explosions appears to be governed by the fraction of energy that is coupled to ultra-relativistic ejecta.

  8. Status of the Milagro $\\gamma$ Ray Observatory

    E-Print Network [OSTI]

    Atkins, R; Berley, D; Chen, M L; Coyne, D G; Delay, R S; Dingus, B L; Dorfan, D E; Ellsworth, R W; Evans, D; Falcone, A D; Fleysher, L; Fleysher, R; Gisler, G; Goodman, J A; Haines, T J; Hoffman, C M; Hugenberger, S; Kelley, L A; Leonor, I; Macri, J R; McConnell, M; McCullough, J F; McEnery, J E; Miller, R S; Mincer, A I; Morales, M F; Némethy, P; Ryan, J M; Schneider, M; Shen, B; Shoup, A L; Sinnis, G; Smith, A J; Sullivan, G W; Thompson, T N; Tümer, T O; Wang, K; Wascko, M O; Westerhoff, S; Williams, D A; Yang, T; Yodh, G B

    2001-01-01T23:59:59.000Z

    The Milagro Gamma Ray Observatory is the world's first large-area water Cherenkov detector capable of continuously monitoring the sky at TeV energies. Located in northern New Mexico, Milagro will perform an all sky survey of the Northern Hemisphere at energies between ~250 GeV and 50 TeV. With a high duty cycle, large detector area (~5000 square meters), and a wide field-of-view (~1 sr), Milagro is uniquely capable of searching for transient and DC sources of high-energy gamma-ray emission. Milagro has been operating since February, 1999. The current status of the Milagro Observatory and initial results will be discussed.

  9. Gamma Ray Bursts in the HAWC Era

    E-Print Network [OSTI]

    Mészáros, Peter; Murase, Kohta; Fox, Derek; Gao, He; Senno, Nicholas

    2015-01-01T23:59:59.000Z

    Gamma-Ray Bursts are the most energetic explosions in the Universe, and are among the most promising for detecting multiple non-electromagnetic signals, including cosmic rays, high energy neutrinos and gravitational waves. The multi-GeV to TeV gamma-ray range of GRB could have significant contributions from hadronic interactions, mixed with more conventional leptonic contributions. This energy range is important for probing the source physics, including overall energetics, the shock parameters and the Lorentz factor. We discuss some of the latest observational and theoretical developments in the field.

  10. Gamma Ray Bursts in the HAWC Era

    E-Print Network [OSTI]

    Peter Mészáros; Katsuaki Asano; Kohta Murase; Derek Fox; He Gao; Nicholas Senno

    2015-06-08T23:59:59.000Z

    Gamma-Ray Bursts are the most energetic explosions in the Universe, and are among the most promising for detecting multiple non-electromagnetic signals, including cosmic rays, high energy neutrinos and gravitational waves. The multi-GeV to TeV gamma-ray range of GRB could have significant contributions from hadronic interactions, mixed with more conventional leptonic contributions. This energy range is important for probing the source physics, including overall energetics, the shock parameters and the Lorentz factor. We discuss some of the latest observational and theoretical developments in the field.

  11. Status of the Milagro Gamma Ray Observatory

    E-Print Network [OSTI]

    R. Atkins; W. Benbow; D. Berley; M. -L. Chen; D. G. Coyne; R. S. Delay; B. L. Dingus; D. E. Dorfan; R. W. Ellsworth; D. Evans; A. Falcone; L. Fleysher; R. Fleysher; G. Gisler; J. A. Goodman; T. J. Haines; C. M. Hoffman; S. Hugenberger; L. A. Kelley; I. Leonor; J. Macri; M. McConnell; J. F. McCullough; J. E. McEnery; R. S. Miller; A. I. Mincer; M. F. Morales; P. Nemethy; J. M. Ryan; M. Schneider; B. Shen; A. Shoup; G. Sinnis; A. J. Smith; G. W. Sullivan; T. N. Thompson; O. T. Tumer; K. Wang; M. O. Wascko; S. Westerhoff; D. A. Williams; T. Yang; G. B. Yodh

    1999-06-24T23:59:59.000Z

    The Milagro Gamma Ray Observatory is the world's first large-area water Cherenkov detector capable of continuously monitoring the sky at TeV energies. Located in northern New Mexico, Milagro will perform an all sky survey of the Northern Hemisphere at energies between ~250 GeV and 50 TeV. With a high duty cycle, large detector area (~5000 square meters), and a wide field-of-view (~1 sr), Milagro is uniquely capable of searching for transient and DC sources of high-energy gamma-ray emission. Milagro has been operating since February, 1999. The current status of the Milagro Observatory and initial results will be discussed.

  12. Observation of the Crab Nebula in Soft Gamma Rays with the Nuclear Compton Telescope

    E-Print Network [OSTI]

    Bandstra, Mark ShenYu

    2010-01-01T23:59:59.000Z

    Gamma-ray bursts . . . . . . . . . . . . . . . . . . . 1.268] G. J. Fishman. The gamma-ray burst capabilities of BATSEOlson. Observations of Gamma- Ray Bursts of Cosmic Origin.

  13. 07/05/2013 21:46Evolution Of Black Holes Compared To Evolution Of Flight -Space News -redOrbit Page 1 of 3http://www.redorbit.com/news/space/1112839583/evolutionary-biology-applied-to-black-hole-manifestation-050713/

    E-Print Network [OSTI]

    Reece, Sarah

    -long Gamma-Ray Bursts Dying Supergiant Stars Implicated in Hours-long Gamma-Ray Bursts NASA\\'s Fermi, Swift See \\'Shockingly Bright\\' Burst NASA\\'s Fermi, Swift See \\'Shockingly Bright\\' Burst Long Day

  14. Ultrahigh Energy Cosmic Rays and Prompt TeV Gamma Rays from Gamma Ray Bursts

    E-Print Network [OSTI]

    Pijushpani Bhattacharjee; Nayantara Gupta

    2003-05-12T23:59:59.000Z

    Gamma Ray Bursts (GRBs) have been proposed as one {\\it possible} class of sources of the Ultrahigh Energy Cosmic Ray (UHECR) events observed up to energies $\\gsim10^{20}\\ev$. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability of the prompt TeV gamma rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole.

  15. High redshift Gamma-Ray Bursts

    E-Print Network [OSTI]

    Salvaterra, R

    2015-01-01T23:59:59.000Z

    Ten years of operations of the Swift satellite have allow us to collect a small sample of long Gamma-Ray Bursts (GRBs) at redshift larger than six. I will review here the present status of this research field and discuss the possible use of GRBs as a fundamental new tool to explore the early Universe, complementary to quasar and galaxy surveys.

  16. Delayed Nickel Decay in Gamma Ray Bursts

    E-Print Network [OSTI]

    G. C. McLaughlin; R. A. M. J. Wijers

    2002-05-19T23:59:59.000Z

    Recently observed emission lines in the X-ray afterglow of gamma ray bursts suggest that iron group elements are either produced in the gamma ray burst, or are present nearby. If this material is the product of a thermonuclear burn, then such material would be expected to be rich in Nickel-56. If the nickel remains partially ionized, this prevents the electron capture reaction normally associated with the decay of Nickel-56, dramatically increasing the decay timescale. Here we examine the consequences of rapid ejection of a fraction of a solar mass of iron group material from the center of a collapsar/hypernova. The exact rate of decay then depends on the details of the ionization and therefore the ejection process. Future observations of iron, nickel and cobalt lines can be used to diagnose the origin of these elements and to better understand the astrophysical site of gamma ray bursts. In this model, the X-ray lines of these iron-group elements could be detected in suspected hypernovae that did not produce an observable gamma ray burst due to beaming.

  17. Gamma-Ray Pulsars: Models and Predictions

    E-Print Network [OSTI]

    Alice K. Harding

    2000-12-12T23:59:59.000Z

    Pulsed emission from gamma-ray pulsars originates inside the magnetosphere, from radiation by charged particles accelerated near the magnetic poles or in the outer gaps. In polar cap models, the high energy spectrum is cut off by magnetic pair production above an energy that is dependent on the local magnetic field strength. While most young pulsars with surface fields in the range B = 10^{12} - 10^{13} G are expected to have high energy cutoffs around several GeV, the gamma-ray spectra of old pulsars having lower surface fields may extend to 50 GeV. Although the gamma-ray emission of older pulsars is weaker, detecting pulsed emission at high energies from nearby sources would be an important confirmation of polar cap models. Outer gap models predict more gradual high-energy turnovers at around 10 GeV, but also predict an inverse Compton component extending to TeV energies. Detection of pulsed TeV emission, which would not survive attenuation at the polar caps, is thus an important test of outer gap models. Next-generation gamma-ray telescopes sensitive to GeV-TeV emission will provide critical tests of pulsar acceleration and emission mechanisms.

  18. Gamma-ray bursts: a Centauro's cry?

    E-Print Network [OSTI]

    Z. K. Silagadze

    2003-06-30T23:59:59.000Z

    A new candidate for the gamma-ray bursts central engine is proposed: if in some energetic cosmic event a macroscopic amount of bubbles of the disoriented chiral condensate can be formed, then their subsequent decays will produce a relativistic fireball without the baryon loading problem. The neutron star to strange star transition is considered as a candidate example of such cosmic event.

  19. Current segmented gamma-ray scanner technology

    SciTech Connect (OSTI)

    Bjork, C.W.

    1987-01-01T23:59:59.000Z

    A new generation of segmented gamma-ray scanners has been developed at Los Alamos for scrap and waste measurements at the Savannah River Plant and the Los Alamos Plutonium Facility. The new designs are highly automated and exhibit special features such as good segmentation and thorough shielding to improve performance.

  20. PoGOLite -The Polarised Gamma-ray Observer

    E-Print Network [OSTI]

    Haviland, David

    PoGOLite - The Polarised Gamma-ray Observer CECILIA MARINI BETTOLO Licentiate Thesis Stockholm, Sweden 2008 #12;#12;Licentiate Thesis PoGOLite - The Polarised Gamma-ray Observer Cecilia Marini Bettolo

  1. Picture of the Week: Gamma-ray bursts, infographic

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    4 Gamma-ray bursts: infographic Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. With the help of sophisticated instruments such as the ground based RAPTOR...

  2. Gamma-ray free-electron lasers: Quantum fluid model

    E-Print Network [OSTI]

    Silva, H M

    2014-01-01T23:59:59.000Z

    A quantum fluid model is used to describe the interacion of a nondegenerate cold relativistic electron beam with an intense optical wiggler taking into account the beam space-charge potential and photon recoil effect. A nonlinear set of coupled equations are obtained and solved numerically. The numerical results shows that in the limit of plasma wave-breaking an ultra-high power radiation pulse are emitted at the$\\gamma$-ray wavelength range which can reach an output intensity near the Schwinger limit depending of the values of the FEL parameters such as detuning and input signal initial phase at the entrance of the interaction region.

  3. Gamma-Ray Bursts, Ultra High Energy Cosmic Rays, and Cosmic Gamma-Ray Background

    E-Print Network [OSTI]

    Tomonori Totani

    1999-04-13T23:59:59.000Z

    We argue that gamma-ray bursts (GRBs) may be the origin of the cosmic gamma-ray background radiation observed in GeV range. It has theoretically been discussed that protons may carry a much larger amount of energy than electrons in GRBs, and this large energy can be radiated in TeV range by synchrotron radiation of ultra-high-energy protons (\\sim 10^{20} eV). The possible detection of GRBs above 10 TeV suggested by the Tibet and HEGRA groups also supports this idea. If this is the case, most of TeV gamma-rays from GRBs are absorbed in intergalactic fields and eventually form GeV gamma-ray background, whose flux is in good agreement with the recent observation.

  4. High Efficiency of Gamma-Ray Bursts Revisited

    E-Print Network [OSTI]

    Y. C. Zou A; Z. G. Dai B

    2007-01-01T23:59:59.000Z

    efficiency of gamma-ray bursts by assuming that the ejecta from the central engine are equally massive and

  5. Analysis of GeV-band gamma-ray emission from SNR RX J1713.7-3946

    E-Print Network [OSTI]

    Federici, S; Telezhinsky, I; Wilhelm, A; Dwarkadas, V V

    2015-01-01T23:59:59.000Z

    RX J1713.7-3946 is the brightest shell-type Supernova remnant (SNR) of the TeV gamma-ray sky. Earlier Fermi-LAT results on low-energy gamma-ray emission suggested that, despite large uncertainties in the background determination, the spectrum is inconsistent with a hadronic origin. We update the GeV-band spectra using improved estimates for the diffuse galactic gamma-ray emission and more than doubled data volume. We further investigate the viability of hadronic emission models for RX J1713.7-3946. We produced a high-resolution map of the diffuse Galactic gamma-ray background corrected for HI self-absorption and used it in the analysis of more than 5~years worth of Fermi-LAT data. We used hydrodynamic scaling relations and a kinetic transport equation to calculate the acceleration and propagation of cosmic-rays in SNR. We then determined spectra of hadronic gamma-ray emission from RX J1713.7-3946, separately for the SNR interior and the cosmic-ray precursor region of the forward shock, and computed flux varia...

  6. High-Energy Neutrinos in Light of Fermi-LAT

    E-Print Network [OSTI]

    Ahlers, Markus

    2015-01-01T23:59:59.000Z

    The production of high-energy astrophysical neutrinos is tightly linked to the emission of hadronic gamma-rays. I will discuss the recent observation of TeV to PeV neutrinos by the IceCube Cherenkov telescope in the context of gamma-ray astronomy. The corresponding energy range of hadronic gamma-rays is not directly accessible by extragalactic gamma-ray astronomy due to interactions with cosmic radiation backgrounds. Nevertheless, the isotropic sub-TeV gamma-ray background observed by the Fermi Large Area Telescope (LAT) contains indirect information from secondary emission produced in electromagnetic cascades and constrains hadronic emission scenarios. On the other hand, observation of PeV gamma-rays would provide a smoking-gun signal for Galactic emission. In general, the cross-correlation of neutrino emission with (extended) Galactic and extragalactic gamma-ray sources will serve as the most sensitive probe for a future identification of neutrino sources.

  7. The Compton Effect--Compton Scattering and Gamma Ray Spectroscopy

    E-Print Network [OSTI]

    Dai, Pengcheng

    The Compton Effect-- Compton Scattering and Gamma Ray Spectroscopy by Dr. James E. Parks Department and procedures for measuring gamma-ray energy distributions, (7) to learn about photomultipliers the interactions of high energy, electromagnetic photon radiation with materials in general. Gamma rays are high

  8. The Biggest Bangs The Mystery of Gamma-Ray Bursts,

    E-Print Network [OSTI]

    Katz, Jonathan I.

    The Biggest Bangs The Mystery of Gamma-Ray Bursts, The Most Violent Explosions in The Universe J. I a Gamma-Ray Burst Kill the Dinosaurs? Will a Burst Kill Us? · Glossary · Sources · Index viii #12;Chapter of these four cameras recorded visible light from a gamma-ray burst as it was happening, which had been the holy

  9. Gamma-Ray Bursts Nuclear Test Ban Treaty, 1963

    E-Print Network [OSTI]

    Harrison, Thomas

    Lecture 18 Gamma-Ray Bursts #12;Nuclear Test Ban Treaty, 1963 First Vela satellite pair launched and their predecessors, Vela 4, discovered the first gamma-ray bursts. The discovery was announced by Klebesadel, Strong, and Olson (ApJ, 182, 85) in 1973. #12;First Gamma-Ray Burst The Vela 5 satellites functioned from July, 1969

  10. The Biggest Bangs The Mystery of Gamma-Ray Bursts,

    E-Print Network [OSTI]

    Katz, Jonathan I.

    The Biggest Bangs The Mystery of Gamma-Ray Bursts, The Most Violent Explosions in The Universe J. I. Did a Gamma-Ray Burst Kill the Dinosaurs? Will a Burst Kill Us? #15; Glossary #15; Sources #15; Index. On January 23, 1999, one of these four cameras recorded visible light from a gamma-ray burst

  11. GammaRay Bursts: Old and New JOCHEN GREINER

    E-Print Network [OSTI]

    Greiner, Jochen

    Gamma­Ray Bursts: Old and New JOCHEN GREINER Astrophysikalisches Institut Potsdam, 14482 Potsdam, Germany (jgreiner@aip.de) ABSTRACT. Gamma­ray bursts are sudden releases of energy that for a duration of a few seconds outshine even huge galaxies. 30 years after the first detection of a gamma­ray burst

  12. Unveiling the nature of the gamma-ray emitting AGN PKS 0521-36

    E-Print Network [OSTI]

    D'Ammando, F; Tavecchio, F; Ghisellini, G; Torresi, E; Giroletti, M; Raiteri, C M; Grandi, P; Aller, M; Aller, H; Gurwell, M A; Malaguti, G; Pian, E; Tosti, G

    2015-01-01T23:59:59.000Z

    PKS 0521-36 is an Active Galactic Nucleus (AGN) with uncertain classification. We investigate the properties of this source from radio to gamma rays. The broad emission lines in the optical and UV bands and steep radio spectrum indicate a possible classification as an intermediate object between broad-line radio galaxies (BLRG) and steep spectrum radio quasars (SSRQ). On pc-scales PKS 0521-36 shows a knotty structure similar to misaligned AGN. The core dominance and the gamma-ray properties are similar to those estimated for other SSRQ and BLRG detected in gamma rays, suggesting an intermediate viewing angle with respect to the observer. In this context the flaring activity detected from this source by Fermi-LAT between 2010 June and 2012 February is very intriguing. We discuss the gamma-ray emission of this source in the framework of the structured jet scenario, comparing the spectral energy distribution (SED) of the flaring state in 2010 June with that of a low state. We present three alternative models cor...

  13. Gamma-ray novae as probes of relativistic particle acceleration at non-relativistic shocks

    E-Print Network [OSTI]

    Metzger, Brian D; Vurm, Indrek; Hascoet, Romain; Beloborodov, Andrei M; Chomiuk, Laura

    2015-01-01T23:59:59.000Z

    The Fermi LAT discovery that classical novae produce >100 MeV gamma-rays establishes that shocks and relativistic particle acceleration are key features of these events. These shocks are likely to be radiative due to the high densities of the nova ejecta at early times coincident with the gamma-ray emission. Thermal X-rays radiated behind the shock are absorbed by neutral gas and reprocessed into optical emission, similar to Type IIn (interacting) supernovae. The ratio of gamma-ray and optical luminosities, L_gam/L_opt, thus sets a lower limit on the fraction of the shock power used to accelerate relativistic particles, e_nth. The measured values of L_gam/L_opt for two classical novae, V1324 Sco and V339 Del, constrains e_nth > 1e-2 and > 1e-3, respectively. Inverse Compton models for the gamma-ray emission are disfavored given the low electron acceleration efficiency, e_nth ~ 1e-4-1e-3, inferred from observations of Galactic cosmic rays and particle-in-cell (PIC) numerical simulations. Recent hybrid PIC simu...

  14. MilagroA TeV Observatory for Gamma Ray Bursts

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    Milagro­A TeV Observatory for Gamma Ray Bursts B.L. Dingus and the Milagro Collaboration Los energy gamma-rays from gamma-ray bursts. The highest energy gamma rays supply very strong constraints on the nature of gamma-ray burst sources as well as fundamental physics. Because the highest energy gamma-rays

  15. Simulated observations of gamma-ray bursts with GLAST

    SciTech Connect (OSTI)

    Bonnell, J. T.; Norris, J. P. [Code 661, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Dingus, B. L. [Department of Physics, University of Utah, Salt Lake City, Utah 84112 (United States); Scargle, J. D. [NASA Ames Research Center, MS 245-3, Moffett Field, California 94035 (United States)

    1998-05-16T23:59:59.000Z

    The Gamma-ray Large Area Space Telescope (GLAST) will incorporate high sensitivity, large field of view, and precision tracker technology, providing arc-minute localizations of gamma-ray bursts (GRBs) and exploring GRB physics up to {approx}100 GeV. We have simulated the response of GLAST to GRBs with power-law spectra extending to GeV energies to determine the detailed burst localization capability. The simulated properties of GRBs are based on the BATSE peak flux and duration distributions. GLAST's hodoscopic calorimeter design has sufficiently good angular resolution and discrimination power against cosmic rays that >1 GeV gammas which are only detected in the calorimeter may be utilized for bright sources such as GRBs. Our results indicate that GLAST will detect and image {approx}230 GRBs yr{sup -1} with sensitivity to {approx}100 GeV for {approx}20 bursts yr{sup -1}. Many bright burst localizations will be comparable in size to the current InterPlanetary Network error boxes thus probing the cosmological burst parameter space at nearby redshifts and enabling counterpart searches at all lower energies.

  16. Neutron-driven gamma-ray laser

    DOE Patents [OSTI]

    Bowman, Charles D. (Los Alamos, NM)

    1990-01-01T23:59:59.000Z

    A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 .ANG. when subjected to an intense neutron flux of about 400 eV neutrons. A 250 .ANG. thick layer of Be is provided between two layers of 100 .ANG. thick layer of .sup.57 Co and these layers are supported on a foil substrate. The coated foil is coiled to form the lasing cylinder. Under the neutron flux .sup.57 Co becomes .sup.58 Co by neutron absorption. The .sup.58 Co then decays to .sup.57 Fe by 1.6 MeV proton emission. .sup.57 Fe then transitions by mesne decay to a population inversion for lasing action at 14.4 keV. Recoil from the proton emission separates the .sup.57 Fe from the .sup.57 Co and into the Be, where Mossbauer emission occurs at a gamma-ray wavelength.

  17. Fissile interrogation using gamma rays from oxygen

    DOE Patents [OSTI]

    Smith, Donald; Micklich, Bradley J.; Fessler, Andreas

    2004-04-20T23:59:59.000Z

    The subject apparatus provides a means to identify the presence of fissionable material or other nuclear material contained within an item to be tested. The system employs a portable accelerator to accelerate and direct protons to a fluorine-compound target. The interaction of the protons with the fluorine-compound target produces gamma rays which are directed at the item to be tested. If the item to be tested contains either a fissionable material or other nuclear material the interaction of the gamma rays with the material contained within the test item with result in the production of neutrons. A system of neutron detectors is positioned to intercept any neutrons generated by the test item. The results from the neutron detectors are analyzed to determine the presence of a fissionable material or other nuclear material.

  18. Gamma-Ray Bursts: Progress, Problems & Prospects

    E-Print Network [OSTI]

    Bing Zhang; Peter Meszaros

    2003-11-13T23:59:59.000Z

    The cosmological gamma-ray burst (GRB) phenomenon is reviewed. The broad observational facts and empirical phenomenological relations of the GRB prompt emission and afterglow are outlined. A well-tested, successful fireball shock model is introduced in a pedagogical manner. Several important uncertainties in the current understanding of the phenomenon are reviewed, and prospects of how future experiments and extensive observational and theoretical efforts may address these problems are discussed.

  19. Gamma-Ray Line Observations with RHESSI

    E-Print Network [OSTI]

    David M. Smith

    2004-04-30T23:59:59.000Z

    The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has been observing gamma-ray lines from the Sun and the Galaxy since its launch in February 2002. Here I summarize the status of RHESSI observations of solar lines (nuclear de-excitation, neutron capture, and positron annihilation), the lines of $^{26}$Al and $^{60}$Fe from the inner Galaxy, and the search for positron annihilation in novae.

  20. EXPLORING THE CENTRAL SUB-PARSEC REGION OF THE {gamma}-RAY BRIGHT RADIO GALAXY 3C 84 WITH VLBA AT 43 GHz IN THE PERIOD OF 2002-2008

    SciTech Connect (OSTI)

    Suzuki, Kenta [Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Nagai, Hiroshi; Kino, Motoki; Kobayashi, Hideyuki [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Kataoka, Jun [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Asada, Keiichi; Inoue, Makoto [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan, R.O.C. (China); Doi, Akihiro [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai 3-1-1, Chuo-ku, Sagamihara 252-5210 (Japan); Orienti, Monica; Giovannini, Gabriele; Giroletti, Marcello [INAF Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna (Italy); Laehteenmaeki, Anne; Tornikoski, Merja; Leon-Tavares, Jonathan [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FIN-02540 Kylmaelae (Finland); Bach, Uwe [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Kameno, Seiji [Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan)

    2012-02-20T23:59:59.000Z

    Following the discovery of a new radio component right before the GeV {gamma}-ray detection since 2008 August by the Fermi Gamma-ray Space Telescope, we present a detailed study of the kinematics and light curve on the central sub-parsec scale of 3C 84 using the archival Very Long Baseline Array 43 GHz data covering the period between 2002 January and 2008 November. We find that the new component 'C3', previously reported by the observations with the Very Long Baseline Interferometer Exploration of Radio Astrometry, was already formed in 2003. The flux density of C3 increases moderately until 2008, and then it becomes brighter rapidly after 2008. The radio core, C1, also shows a similar trend. The apparent speed of C3 with reference to the core C1 shows moderate acceleration from 0.10c to 0.47c between 2003 November and 2008 November, but is still sub-relativistic. We further try to fit the observed broadband spectrum by the one-zone synchrotron self-Compton model using the measured apparent speed of C3. The fit can reproduce the observed {gamma}-ray emission, but does not agree with the observed radio spectral index between 22 and 43 GHz.

  1. Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1

    SciTech Connect (OSTI)

    Ajello, M.; Allafort, A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Baldini, L.; /INFN, Pisa; Ballet, J.; /AIM, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; Blandford, R.D.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari Polytechnic /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Buson, S.; /INFN, Padua /Padua U.; Caliandro, G.A.; /CSIC, Catalunya; Cameron, R.A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Caraveo, P.A.; /IASF, Milan /AIM, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Unlisted, US /Naval Research Lab, Wash., D.C. /Perugia U. /ASDC, Frascati /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /ASDC, Frascati /Udine U. /INFN, Trieste /Bari Polytechnic /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Udine U. /INFN, Trieste /Trieste Observ. /Hiroshima U. /Nagoya U. /Bari Polytechnic /INFN, Bari /INFN, Bari /ASDC, Frascati /INFN, Perugia /Perugia U. /Bari Polytechnic /INFN, Bari /ASDC, Frascati /Bari Polytechnic /INFN, Bari /Bologna Observ. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Naval Research Lab, Wash., D.C. /Alabama U., Huntsville /CSIC, Catalunya /Hiroshima U. /NASA, Goddard /Hiroshima U.; /more authors..

    2012-09-14T23:59:59.000Z

    We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 {+-} 0.6 (stat) {+-} 1.2 (sys) GeV, and photon indices of 2.10 {+-} 0.06 (stat) {+-} 0.10 (sys) below the break and 2.70 {+-} 0.12 (stat) {+-} 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of p0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

  2. Optical spectroscopic observations of gamma-ray blazar candidates IV. Results of the 2014 follow-up campaign

    E-Print Network [OSTI]

    Ricci, F; Landoni, M; D'Abrusco, R; Milisavljevic, D; Stern, D; Masetti, N; Paggi, A; Smith, Howard A; Tosti, G

    2015-01-01T23:59:59.000Z

    The extragalactic gamma-ray sky is dominated by the emission arising from blazars, one of the most peculiar classes of radio-loud active galaxies. Since the launch of Fermi several methods were developed to search for blazars as potential counterparts of unidentified gamma-ray sources (UGSs). To confirm the nature of the selected candidates, optical spectroscopic observations are necessary. In 2013 we started a spectroscopic campaign to investigate gamma-ray blazar candidates selected according to different procedures. The main goals of our campaign are: 1) to confirm the nature of these candidates, and 2) whenever possible determine their redshifts. Optical spectroscopic observations will also permit us to verify the robustness of the proposed associations and check for the presence of possible source class contaminants to our counterpart selection. This paper reports the results of observations carried out in 2014 in the Northern hemisphere with Kitt Peak National Observatory (KPNO) and in the Southern hemi...

  3. Very high energy gamma-ray follow-up observations of novae and dwarf novae with the MAGIC telescopes

    E-Print Network [OSTI]

    Sitarek, J; Lopez-Coto, R; Wilhelmi, E de Ona; Desiante, R; Longo, F; Hays, E

    2015-01-01T23:59:59.000Z

    In the last few years the Fermi -LAT instrument has detected GeV gamma-ray emission from a few novae. Such GeV emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. It is expected that hadrons can be accelerated in the same conditions, but reaching much higher energies. They can produce a second component in the gamma-ray spectrum at TeV energies. We performed follow-up observations of selected novae and dwarf novae in a search of the second component in the gamma-ray spectrum. This can shed light on the acceleration process of leptons and hadrons in nova explosions. We have performed observations with the MAGIC telescopes of 3 sources, a symbiotic nova YY Her, a dwarf nova ASASSN-13ax and a classical nova V339 Del shortly after their outbursts.

  4. Gamma Ray Bursts, The Principle of Relative Locality and Connection Normal Coordinates

    E-Print Network [OSTI]

    A. E. McCoy

    2012-01-04T23:59:59.000Z

    The launch of the Fermi telescope in 2008 opened up the possibility of measuring the energy dependence of the speed of light by considering the time delay in the arrival of gamma ray bursts emitted simultaneously from very distant sources.The expected time delay between the arrival of gamma rays of significantly different energies as predicted by the framework of relative locality has already been calculated in Riemann normal coordinates. In the following, we calculate the time delay in more generality and then specialize to the connection normal coordinate system as a check that the results are coordinate independent. We also show that this result does not depend on the presence of torsion.

  5. EPISODIC JETS AS THE CENTRAL ENGINE OF GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Yuan Feng [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Zhang Bing, E-mail: fyuan@shao.ac.cn, E-mail: zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States)

    2012-09-20T23:59:59.000Z

    Most gamma-ray bursts (GRBs) have erratic light curves, which demand that the GRB central engine launches an episodic outflow. Recent Fermi observations of some GRBs indicate a lack of the thermal photosphere component as predicted by the baryonic fireball model, which suggests a magnetic origin of GRBs. Given that powerful episodic jets have been observed along with continuous jets in other astrophysical black hole systems, here we propose an intrinsically episodic, magnetically dominated jet model for the GRB central engine. Accumulation and eruption of free magnetic energy in the corona of a differentially rotating, turbulent accretion flow around a hyperaccreting black hole lead to ejections of episodic, magnetically dominated plasma blobs. These blobs are accelerated magnetically, collide with each other at large radii, trigger rapid magnetic reconnection and turbulence, efficient particle acceleration, and radiation, and power the observed episodic prompt gamma-ray emission from GRBs.

  6. Wormholes, Gamma Ray Bursts and the Amount of Negative Mass in the Universe

    E-Print Network [OSTI]

    Diego F. Torres; Gustavo E. Romero; Luis A. Anchordoqui

    1998-05-19T23:59:59.000Z

    In this essay, we assume that negative mass objects can exist in the extragalactic space and analyze the consequences of their microlensing on light from distant Active Galactic Nuclei. We find that such events have very similar features to some observed Gamma Ray Bursts and use recent satellite data to set an upper bound to the amount of negative mass in the universe.

  7. Quantum mechanics in phase space: First order comparison between the Wigner and the Fermi function

    E-Print Network [OSTI]

    G. Benenti; G. Strini

    2009-09-08T23:59:59.000Z

    The Fermi g_F(x,p) function provides a phase space description of quantum mechanics conceptually different from that based on the the Wigner function W(x,p). In this paper, we show that for a peaked wave packet the g_F(x,p)=0 curve approximately corresponds to a phase space contour level of the Wigner function and provides a satisfactory description of the wave packet's size and shape. Our results show that the Fermi function is an interesting tool to investigate quantum fluctuations in the semiclassical regime.

  8. Gamma-ray burst interaction with dense interstellar medium

    E-Print Network [OSTI]

    Maxim Barkov; Gennady Bisnovatyi-Kogan

    2004-10-07T23:59:59.000Z

    Interaction of cosmological gamma ray burst radiation with the dense interstellar medium of host galaxy is considered. Gas dynamical motion of interstellar medium driven by gamma ray burst is investigated in 2D approximation for different initial density distributions of host galaxy matter and different total energy of gamma ray burst. The maximum velocity of motion of interstellar medium is $1.8\\cdot10^4$ km/s. Light curves of gamma ray burst afterglow are calculated for set of non homogeneous density, distribution gamma ray burst total energy, and different viewing angles. Spectra of gamma ray burst afterglow are modeled taking into account conversion of hard photons (soft X-ray, hard UV) to soft UV and optics photons.

  9. X-Ray Observations of Gamma-Ray Burst Afterglows

    E-Print Network [OSTI]

    Filippo Frontera

    2004-06-25T23:59:59.000Z

    The discovery by the BeppoSAX satellite of X-ray afterglow emission from the gamma-ray burst which occurred on 28 February 1997 produced a revolution in our knowledge of the gamma-ray burst phenomenon. Along with the discovery of X-ray afterglows, the optical afterglows of gamma-ray bursts were discovered and the distance issue was settled, at least for long $\\gamma$-ray bursts. The 30 year mystery of the gamma-ray burst phenomenon is now on the way to solution. Here I rewiew the observational status of the X-ray afterglow emission, its mean properties (detection rate, continuum spectra, line features, and light curves), and the X-ray constraints on theoretical models of gamma-ray bursters and their progenitors. I also discuss the early onset afterglow emission, the remaining questions, and the role of future X-ray afterglow observations.

  10. Can Naked Singularities Yield Gamma Ray Bursts?

    E-Print Network [OSTI]

    H. M. Antia

    1998-07-09T23:59:59.000Z

    Gamma-ray bursts are believed to be the most luminous objects in the Universe. There has been some suggestion that these arise from quantum processes around naked singularities. The main problem with this suggestion is that all known examples of naked singularities are massless and hence there is effectively no source of energy. It is argued that a globally naked singularity coupled with quantum processes operating within a distance of the order of Planck length of the singularity will probably yield energy burst of the order of M_pc^2\\approx2\\times 10^{16} ergs, where M_p is the Planck mass.

  11. Puzzles of Galactic continuum gamma rays

    E-Print Network [OSTI]

    I. V. Moskalenko; A. W. Strong

    1998-11-14T23:59:59.000Z

    Inverse Compton scattering appears to play a more important role in the diffuse Galactic continuum emission than previously thought, from MeV to GeV energies. We compare models having a large inverse Compton component with EGRET data, and find good agreement in the longitude and latitude distributions at low and high energies. We test an alternative explanation for the >1 GeV gamma-ray excess, the hard nucleon spectrum, using secondary antiprotons and positrons. At lower energies to fit the COMPTEL and OSSE data as diffuse emission requires either a steep upturn in the electron spectrum below 200 MeV or a population of discrete sources.

  12. Gamma-Ray Bursts observed by INTEGRAL

    E-Print Network [OSTI]

    S. Mereghetti

    2003-12-12T23:59:59.000Z

    During the first six months of operations, six Gamma Ray Bursts (GRBs) have been detected in the field of view of the INTEGRAL instruments and localized by the INTEGRAL Burst Alert System (IBAS): a software for the automatic search of GRBs and the rapid distribution of their coordinates. I describe the current performances of IBAS and review the main results obtained so far. The coordinates of the latest burst localized by IBAS, GRB 031203, have been distributed within 20 s from the burst onset and with an uncertainty radius of only 2.7 arcmin.

  13. High-Energy Cosmology: gamma rays and neutrinos from beyond the galaxy

    E-Print Network [OSTI]

    Charles D. Dermer

    2006-11-06T23:59:59.000Z

    Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new discoveries from Swift and HESS, results from MAGIC and VERITAS starting to be reported, the upcoming launches of the gamma-ray space telescopes GLAST and AGILE, and anticipated data releases from IceCube and Auger. A formalism for calculating statistical properties of cosmological gamma-ray sources is presented. Application is made to model calculations of the statistical distributions of gamma-ray and neutrino emission from (i) beamed sources, specifically, long-duration GRBs, blazars, and extagalactic microquasars, and (ii) unbeamed sources, including normal galaxies, starburst galaxies and clusters. Expressions for the integrated intensities of faint beamed and unbeamed high-energy radiation sources are also derived. A toy model for the background intensity of radiation from dark-matter annihilation taking place in the early universe is constructed. Estimates for the gamma-ray fluxes of local group galaxies, starburst, and infrared luminous galaxies are briefly reviewed. Because the brightest extragalactic gamma-ray sources are flaring sources, and these are the best targets for sources of PeV -- EeV neutrinos and ultra-high energy cosmic rays, rapidly slewing all-sky telescopes like MAGIC and an all-sky gamma-ray observatory beyond Milagro will be crucial for optimal science return in the multi-messenger age.

  14. Gamma-ray Bursts as Probes of Galaxy Evolution

    E-Print Network [OSTI]

    ?umer, Slobodan

    Gamma-ray Bursts as Probes of Galaxy Evolution Daniele Malesani, Dark Cosmology Centre and the X of the "Universe") #12;What is a gamma-ray burst? Brief (ms - min) and intense (~10-7 erg cm­2 s­1 ) burst of soft to ongoing star formation "Naked-eye" GRB 080319B GRBs explode within star-forming galaxies Gamma-ray bursts

  15. Gamma Ray Bursts, Neutron Star Quakes, and the Casimir Effect

    E-Print Network [OSTI]

    C. Carlson; T. Goldman; J. Perez-Mercader

    1994-11-25T23:59:59.000Z

    We propose that the dynamic Casimir effect is a mechanism that converts the energy of neutron starquakes into $\\gamma$--rays. This mechanism efficiently produces photons from electromagnetic Casimir energy released by the rapid motion of a dielectric medium into a vacuum. Estimates based on the cutoff energy of the gamma ray bursts and the volume involved in a starquake indicate that the total gamma ray energy emission is consonant with observational requirements.

  16. Nuclear Criticality as a Contributor to Gamma Ray Burst Events

    E-Print Network [OSTI]

    Robert Bruce Hayes

    2013-01-15T23:59:59.000Z

    Most gamma ray bursts are able to be explained using supernovae related phenomenon. Some measured results still lack compelling explanations and a contributory cause from nuclear criticality is proposed. This is shown to have general properties consistent with various known gamma ray burst properties. The galactic origin of fast rise exponential decay gamma ray bursts is considered a strong candidate for these types of events.

  17. A panchromatic view of relativistic jets in gamma-ray emitting narrow-line Seyfert 1 galaxies

    E-Print Network [OSTI]

    D'Ammando, F; Finke, J; Giroletti, M; Larsson, J

    2015-01-01T23:59:59.000Z

    Before the launch of the Fermi satellite only two classes of Active Galactic Nuclei (AGN) were known to generate relativistic jets and thus to emit up to the gamma-ray energy range: blazars and radio galaxies, both hosted in giant elliptical galaxies. The first four years of observations by the Large Area Telescope (LAT) on board Fermi confirmed that these two populations represent the most numerous identified sources in the extragalactic gamma-ray sky, but the discovery of variable gamma-ray emission from 5 radio-loud Narrow-Line Seyfert 1 (NLSy1) galaxies revealed the presence of a possible emerging third class of AGN with relativistic jets. Considering that NLSy1 are thought to be hosted in spiral galaxies, this finding poses intriguing questions about the nature of these objects, the knowledge of the development of relativistic jets, and the evolution of radio-loud AGN. In this context, the study of the radio-loud NLSy1 from radio to gamma-rays has received increasing attention. Here we discuss the radio-...

  18. atmospheric gamma rays: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Cherenkov telescope for gamma-ray astronomy. STACEE uses the large mirror area of a solar heliostat facility to achieve a low energy threshold. A prototype experiment which...

  19. CONSTRAINTS ON THE SYNCHROTRON EMISSION MECHANISM IN GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Beniamini, Paz; Piran, Tsvi, E-mail: paz.beniamini@mail.huji.ac.il, E-mail: tsvi.piran@mail.huji.ac.il [Racah Institute for Physics, Hebrew University, Jerusalem 91904 (Israel)

    2013-05-20T23:59:59.000Z

    We reexamine the general synchrotron model for gamma-ray bursts' (GRBs') prompt emission and determine the regime in the parameter phase space in which it is viable. We characterize a typical GRB pulse in terms of its peak energy, peak flux, and duration and use the latest Fermi observations to constrain the high-energy part of the spectrum. We solve for the intrinsic parameters at the emission region and find the possible parameter phase space for synchrotron emission. Our approach is general and it does not depend on a specific energy dissipation mechanism. Reasonable synchrotron solutions are found with energy ratios of 10{sup -4} < {epsilon}{sub B}/{epsilon}{sub e} < 10, bulk Lorentz factor values of 300 < {Gamma} < 3000, typical electrons' Lorentz factor values of 3 Multiplication-Sign 10{sup 3} < {gamma}{sub e} < 10{sup 5}, and emission radii of the order 10{sup 15} cm < R < 10{sup 17} cm. Most remarkable among those are the rather large values of the emission radius and the electron's Lorentz factor. We find that soft (with peak energy less than 100 keV) but luminous (isotropic luminosity of 1.5 Multiplication-Sign 10{sup 53}) pulses are inefficient. This may explain the lack of strong soft bursts. In cases when most of the energy is carried out by the kinetic energy of the flow, such as in the internal shocks, the synchrotron solution requires that only a small fraction of the electrons are accelerated to relativistic velocities by the shocks. We show that future observations of very high energy photons from GRBs by CTA could possibly determine all parameters of the synchrotron model or rule it out altogether.

  20. Radio flares from gamma-ray bursts

    E-Print Network [OSTI]

    Kopac, D; Kobayashi, S; Virgili, F J; Harrison, R; Japelj, J; Guidorzi, C; Melandri, A; Gomboc, A

    2015-01-01T23:59:59.000Z

    We present predictions of centimeter and millimeter radio emission from reverse shocks in the early afterglows of gamma-ray bursts with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parametrization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. (2007) and Melandri et al. (2010) in which the typical frequency of the reverse shock was suggested to lie at radio, rather than optical wavelengths at early times, we show that the brightest and most distinct reverse-shock radio signatures are detectable up to 0.1 -- 1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later opt...

  1. Gamma Ray Fresnel lenses - why not?

    E-Print Network [OSTI]

    G. K. Skinner

    2006-02-03T23:59:59.000Z

    Fresnel lenses offer the possibility of concentrating the flux of X-rays or gamma-rays flux falling on a geometric area of many square metres onto a focal point which need only be a millimetre or so in diameter (and which may even be very much smaller). They can do so with an efficiency that can approach 100%, and yet they are easily fabricated and have no special alignment requirements. Fresnel lenses can offer diffraction-limited angular resolution, even in a domain where that limit corresponds to less than a micro second of arc. Given all these highly desirable attributes, it is natural to ask why Fresnel gamma ray lenses are not already being used, or at least why there is not yet any mission that plans to use the technology. Possible reasons (apart from the obvious one that nobody thought of doing so) include the narrow bandwidth of simple Fresnel lenses, their very long focal length, and the problems of target finding. It is argued that none of these is a "show stopper" and that this technique should be seriously considered for nuclear astrophysics.

  2. DIFFUSE PeV NEUTRINOS FROM GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Liu, Ruo-Yu; Wang, Xiang-Yu [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)] [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2013-04-01T23:59:59.000Z

    The IceCube Collaboration recently reported the potential detection of two cascade neutrino events in the energy range 1-10 PeV. We study the possibility that these PeV neutrinos are produced by gamma-ray bursts (GRBs), paying special attention to the contribution by untriggered GRBs that elude detection due to their low photon flux. Based on the luminosity function, rate distribution with redshift and spectral properties of GRBs, we generate, using a Monte Carlo simulation, a GRB sample that reproduces the observed fluence distribution of Fermi/GBM GRBs and an accompanying sample of untriggered GRBs simultaneously. The neutrino flux of every individual GRB is calculated in the standard internal shock scenario, so that the accumulative flux of the whole samples can be obtained. We find that the neutrino flux in PeV energies produced by untriggered GRBs is about two times higher than that produced by the triggered ones. Considering the existing IceCube limit on the neutrino flux of triggered GRBs, we find that the total flux of triggered and untriggered GRBs can reach at most a level of {approx}10{sup -9} GeV cm{sup -2} s{sup -1} sr{sup -1}, which is insufficient to account for the reported two PeV neutrinos. Possible contributions to diffuse neutrinos by low-luminosity GRBs and the earliest population of GRBs are also discussed.

  3. A New Determination Of The Diffuse Galactic and Extragalactic Gamma-Ray Emission

    E-Print Network [OSTI]

    Moskalenko, Igor V.

    for the distribution of galactic diffuse gamma-rays. We compare different propagation models with gamma-ray spectraA New Determination Of The Diffuse Galactic and Extragalactic Gamma-Ray Emission Andrew W. Strong1 for the apparent excess emission observed at GeV gamma-rays. We find that a population of hard-spectrum gamma-ray

  4. X-RAYRICH GAMMA-RAY BURSTS, PHOTOSPHERES, AND VARIABILITY P. Meszaros,1,2

    E-Print Network [OSTI]

    Zhang, Bing

    X-RAY­RICH GAMMA-RAY BURSTS, PHOTOSPHERES, AND VARIABILITY P. Me´sza´ros,1,2 E. Ramirez-Ruiz,3 M. J of the observational gamma-ray variability-luminosity relation. Subject headings: gamma rays: bursts -- radiation mechanisms: nonthermal 1. INTRODUCTION Gamma-ray burst (GRB) light curves at gamma-ray ener- gies are often

  5. OBSERVATIONS OF THE PROMPT GAMMA-RAY EMISSION OF GRB 070125 Eric C. Bellm,1

    E-Print Network [OSTI]

    California at Berkeley, University of

    2007 November 13; accepted 2008 July 25 ABSTRACT The long, bright gamma-ray burst GRB 070125: gamma rays: bursts 1. INTRODUCTION The prompt gamma-ray emission of gamma-ray bursts (GRBs) is the mostOBSERVATIONS OF THE PROMPT GAMMA-RAY EMISSION OF GRB 070125 Eric C. Bellm,1 Kevin Hurley,1 Valentin

  6. Study of Celestial Objects with Very High Energy Gamma Rays CANGAROO III

    E-Print Network [OSTI]

    Enomoto, Ryoji

    ), the doppler boosting of secondary gamma-rays is sufficient to produce TeV gamma-rays. Gamma-ray bursts: Fireballs expanding with relativistic speed explain gamma-ray bursts at cosmological distancesStudy of Celestial Objects with Very High Energy Gamma Rays CANGAROO III Project Description

  7. Search for GeV Emission from Gamma-Ray Bursts Using Milagro Scaler Data

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    Search for GeV Emission from Gamma-Ray Bursts Using Milagro Scaler Data D. A. Williams to search for high energy emission from a sample of 98 gamma-ray bursts (GRB) detected from January 2000: gamma-ray sources; gamma-ray bursts; astronomical observations: gamma-ray PACS: 98.70.Rz,95.85.Pw Air

  8. The First 100 LAT Gamma-Ray Bursts: A New Detection Algorithm and Pass 8

    E-Print Network [OSTI]

    Vianello, Giacomo

    2015-01-01T23:59:59.000Z

    Observations of Gamma-Ray Bursts with the Fermi Large Area Telescope have prompted theoretical advances and posed big challenges in the understanding of such extreme sources, despite the fact that GRB emission above 100 MeV is a fairly rare event. The first Fermi/LAT GRB catalog, published a year ago, presented 28 detections out of ~300 bursts detected by the Fermi Gamma-Ray Burst Monitor (GBM) within the LAT field of view. Building on the results from that work and on recent development in the understanding of the systematic errors on GBM localizations, we developed a new detection algorithm which increased the number of detections by 40 %. Even more recently the development of the new event analysis for the LAT ("Pass 8") has increased the number of detections within the first 3 years of the mission to 45, up 50 % with respect to the published catalog. The second LAT GRB catalog, in preparation, will cover more than 6 years of the mission and will break the barrier of 100 detected GRBs, a more than 20-fold ...

  9. Hints of the jet composition in gamma-ray bursts from dissipative photosphere models

    E-Print Network [OSTI]

    Veres, Péter

    2015-01-01T23:59:59.000Z

    We present a model for gamma-ray bursts where a dissipative photosphere provides the usual spectral peak around MeV energies accompanied by a subdominant thermal component. We treat the initial acceleration of the jet in a general way, allowing for magnetic field- and baryon dominated outflows. In this model, the GeV emission associated with GRBs observed by Fermi LAT, arises as the interaction of photospheric radiation and the shocked electrons at the deceleration radius. Through recently discovered correlations between the thermal and non-thermal peaks within individual bursts, we are able to infer whether the jet was Poynting flux or baryon dominated.

  10. ON THE LACK OF TIME DILATION SIGNATURES IN GAMMA-RAY BURST LIGHT CURVES

    SciTech Connect (OSTI)

    Kocevski, Daniel [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025 (United States); Petrosian, Vahe [Center for Space Science and Astrophysics, Varian 302c, Stanford University, Stanford, CA 94305 (United States)

    2013-03-10T23:59:59.000Z

    We examine the effects of time dilation on the temporal profiles of gamma-ray burst (GRB) pulses. By using prescriptions for the shape and evolution of prompt gamma-ray spectra, we can generate a simulated population of single-pulsed GRBs at a variety of redshifts and observe how their light curves would appear to a gamma-ray detector here on Earth. We find that the observer frame duration of individual pulses does not increase with redshift as 1 + z, which one would expect from cosmological expansion. This time dilation is masked by an opposite and often stronger effect: with increasing redshift and decreasing signal-to-noise ratio only the brightest portion of the light curve can be detected. The results of our simulation are consistent with the fact that the simple time dilation of GRB light curves has not materialized in either the Swift or Fermi detected GRBs with known redshift. We show that the measured durations and associated E{sub iso} estimates for GRBs detected near the instrument's detection threshold should be considered lower limits to the true values. Furthermore, we conclude that attempts at distinguishing between long and short GRBs, at even moderate redshifts, cannot be done based on a burst's temporal properties alone.

  11. The cosmic X-ray and gamma-ray background from dark matter annihilation

    E-Print Network [OSTI]

    Zavala, Jesus; Slatyer, Tracy R; Loeb, Abraham; Springel, Volker

    2011-01-01T23:59:59.000Z

    (Abridged) The extragalactic background light (EBL) observed at multiple wavelengths is a promising tool to probe the nature of dark matter since it might contain a significant contribution from gamma-rays produced promptly by dark matter annihilation. Additionally, the electrons and positrons produced in the annihilation give energy to the CMB photons to populate the EBL with X-rays and gamma-rays. We here create full-sky maps of the radiation from both of these contributions using the high-resolution Millennium-II simulation. We use upper limits on the contributions of unknown sources to the EBL to constrain the intrinsic properties of dark matter using a model-independent approach that can be employed as a template to test different particle physics models (including those with a Sommerfeld enhancement). These upper limits are based on observations spanning eight orders of magnitude in energy (from soft X-rays measured by CHANDRA to gamma-rays measured by Fermi), and on expectations for the contributions f...

  12. Jet outflow and gamma-ray emission correlations in S5 0716+714

    E-Print Network [OSTI]

    Rani, B; Marscher, A P; Jorstad, S G; Hodgson, J A; Fuhrmann, L; Zensus, J A

    2014-01-01T23:59:59.000Z

    Using millimeter-very long baseline interferometry (VLBI) observations of the BL Lac object S5 0716+714 from August 2008 to September 2013, we investigate variations in the core flux density and orientation of the sub-parsec scale jet i.e. position angle. The gamma-ray data obtained by the Fermi-LAT (Large Area Telescope) are used to investigate the high-energy flux variations over the same time period. For the first time in any blazar, we report a significant correlation between the gamma-ray flux variations and the position angle (PA) variations in the VLBI jet. The cross-correlation analysis also indicates a positive correlation such that the mm-VLBI core flux density variations are delayed with respect to the gamma-ray flux by 82$\\pm$32 days. This suggests that the high-energy emission is coming from a region located $\\geq$(3.8$\\pm$1.9) parsecs upstream of the mm-VLBI core (closer to the central black hole). These results imply that the observed inner jet morphology has a strong connection with the observ...

  13. Cosmic-ray induced gamma-ray emission from the starburst galaxy NGC 253

    SciTech Connect (OSTI)

    Wang, Xilu; Fields, Brian D. [Department of Astronomy, MC-221, 1002 W. Green Street, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)

    2014-05-09T23:59:59.000Z

    Cosmic rays in galaxies interact with the interstellar medium and give us a direct view of nuclear and particle interactions in the cosmos. For example, cosmic-ray proton interactions with interstellar hydrogen produce gamma rays via PcrPism??{sup 0}???. For a 'normal' star-forming galaxy like the Milky Way, most cosmic rays escape the Galaxy before such collisions, but in starburst galaxies with dense gas and huge star formation rate, most cosmic rays do suffer these interactions [1,2]. We construct a 'thick-target' model for starburst galaxies, in which cosmic rays are accelerated by supernovae, and escape is neglected. This model gives an upper limit to the gamma-ray emission. Only two free parameters are involved in the model: cosmic-ray proton acceleration energy rate from supernova and the proton injection spectral index. The pionic gamma-radiation is calculated from 10 MeV to 10 TeV for the starburst galaxy NGC 253, and compared to Fermi and HESS data. Our model fits NGC 253 well, suggesting that cosmic rays in this starburst are in the thick target limit, and that this galaxy is a gamma-ray calorimeter.

  14. Study of TeV shell supernova remnants at gamma-ray energies

    E-Print Network [OSTI]

    Acero, F; Renaud, M; Ballet, J; Hewitt, J W; Rousseau, R; Tanaka, T

    2015-01-01T23:59:59.000Z

    The breakthrough developments of Cherenkov telescopes in the last decade have led to angular resolution of 0.1{\\deg} and an unprecedented sensitivity. This has allowed the current generation of Cherenkov telescopes to discover a population of supernova remnants (SNRs) radiating in very-high-energy (VHE, E>100 GeV) gamma-rays. A number of those VHE SNRs exhibit a shell-type morphology spatially coincident with the shock front of the SNR. The members of this VHE shell SNR club are RX J1713.7-3946, Vela Jr, RCW 86, SN 1006, and HESS J1731-347. The latter two objects have been poorly studied in high-energy (HE, 0.1 5 sigma. With this Fermi analysis, we now have a complete view of the HE to VHE gamma-ray emission of TeV shell SNRs. All five sources have a hard HE photon index (<1.8) suggesting a common scenario where the bulk of the emission is produced by accelerated electrons radiating from radio to VHE gamma-rays through synchrotron and inverse Compton processes. In addition when correcting for the distance,...

  15. THE BRIGHT GAMMA-RAY BURST OF 2000 FEBRUARY 10: A CASE STUDY OF AN OPTICALLY DARK GAMMA-RAY BURST

    E-Print Network [OSTI]

    Fynbo, Johan

    THE BRIGHT GAMMA-RAY BURST OF 2000 FEBRUARY 10: A CASE STUDY OF AN OPTICALLY DARK GAMMA-RAY BURST L Received 2002 January 16; accepted 2002 June 8 ABSTRACT The gamma-ray burst GRB 000210 had the highest: observations -- gamma-rays: bursts 1. INTRODUCTION It is observationally well established that about half

  16. astrophysical gamma ray: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    astrophysical gamma ray First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Astrophysical Gamma Ray...

  17. aerial gamma ray: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    aerial gamma ray First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Cosmic Rays: What Gamma Rays Can Say...

  18. Gamma-Ray Burst Polarimeter - GAP - aboard the Small Solar Power Sail Demonstrator IKAROS

    E-Print Network [OSTI]

    Yonetoku, D; Gunji, S; Mihara, T; Sakashita, T; Morihara, Y; Kikuchi, Y; Fujimoto, H; Toukairin, N; Kodama, Y; Kubo, S

    2010-01-01T23:59:59.000Z

    The small solar power sail demonstrator "IKAROS" is a Japanese engineering verification spacecraft launched by H-IIA rocket on May 21, 2010 at JAXA Tanegashima Space Center. IKAROS has a huge sail with 20 m in diameter which is made of thin polyimide membrane. This sail converts the solar radiation-pressure into the propulsion force of IKAROS and accelerates the spacecraft. The Gamma-Ray Burst Polarimeter (GAP) aboard IKAROS is the first polarimeter to observe the gamma-ray polarization of Gamma-Ray Bursts (GRBs) during the IKAROS cruising phase. GAP is a tinny detector of 3.8 kg in weight and 17 cm in size with an energy range between 50-300 keV. The GAP detector also plays a role of the interplanetary network (IPN) to determine the GRB direction. The detection principle of gamma-ray polarization is the anisotropy of the Compton scattering. GAP works as the GRB polarimeter with the full coincidence mode between the central plastic and the surrounding CsI detectors. GAP is the first instrument, devoted for th...

  19. Polarization mesurements of gamma ray bursts and axion like particles

    E-Print Network [OSTI]

    Andre Rubbia; Alexander Sakharov

    2008-09-03T23:59:59.000Z

    A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of axion like particles (ALPs). Based on evidences of polarized gamma ray emission detected in several gamma ray bursts we estimated the level of ALPs induced dichroism, which could take place in the magnetized fireball environment of a GRB. This allows to estimate the sensitivity of polarization measurements of GRBs to the ALP-photon coupling. This sensitivity $\\gag\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the ALP mass $m_a=10^{-3}~{\\rm eV}$ and MeV energy spread of gamma ray emission is competitive with the sensitivity of CAST and becomes even stronger for lower ALPs masses.

  20. The supernova/gamma-ray burst/jet connection

    E-Print Network [OSTI]

    Hjorth, Jens

    2013-01-01T23:59:59.000Z

    The observed association between supernovae and gamma-ray bursts represents a cornerstone in our understanding of the nature of gamma-ray bursts. The collapsar model provides a theoretical framework for this connection. A key element is the launch of a bi-polar jet (seen as a gamma-ray burst). The resulting hot cocoon disrupts the star while the 56Ni produced gives rise to radioactive heating of the ejecta, seen as a supernova. In this discussion paper I summarise the observational status of the supernova/gamma-ray burst connection in the context of the 'engine' picture of jet-driven supernovae and highlight SN 2012bz/GRB 120422A -- with its luminous supernova but intermediate high-energy luminosity -- as a possible transition object between low-luminosity and jet gamma-ray bursts. The jet channel for supernova explosions may provide new insight into supernova explosions in general.

  1. Neutrino oscillations and gamma-ray bursts

    E-Print Network [OSTI]

    W. Kluzniak

    1998-07-22T23:59:59.000Z

    If the ordinary neutrinos oscillate into a sterile flavor in a manner consistent with the Super-Kamiokande data on the zenith-angle dependence of atmospheric mu-neutrino flux, an energy sufficient to power a typical cosmic gamma-ray burst (GRB) (about 10^{52} erg) can be carried by sterile neutrinos away from the source and deposited in a region relatively free of baryons. Hence, ultra-relativistic bulk motion (required by the theory of and observations of GRBs and their afterglows) can easily be achieved in the vicinity of plausible sources of GRBs. Oscillations between sterile and ordinary neutrinos would thus provide a solution to the ``baryon-loading problem'' in the theory of GRBs.

  2. Constraining Lorentz violations with Gamma Ray Bursts

    E-Print Network [OSTI]

    Maria Rodriguez Martinez; Tsvi Piran

    2006-05-17T23:59:59.000Z

    Gamma ray bursts are excellent candidates to constrain physical models which break Lorentz symmetry. We consider deformed dispersion relations which break the boost invariance and lead to an energy-dependent speed of light. In these models, simultaneously emitted photons from cosmological sources reach Earth with a spectral time delay that depends on the symmetry breaking scale. We estimate the possible bounds which can be obtained by comparing the spectral time delays with the time resolution of available telescopes. We discuss the best strategy to reach the strongest bounds. We compute the probability of detecting bursts that improve the current bounds. The results are encouraging. Depending on the model, it is possible to build a detector that within several years will improve the present limits of 0.015 m_pl.

  3. Short Gamma-Ray Bursts Are Different

    E-Print Network [OSTI]

    J. P. Norris; J. D. Scargle; J. T. Bonnell

    2001-05-07T23:59:59.000Z

    We analyze BATSE time-tagged event (TTE) data for short gamma-ray bursts (T90 duration burst. Performing the cross-correlation between two energy bands, we measure an average lag ~ 20-40 x shorter than for long bursts, and a lag distribution close to symmetric about zero - unlike long bursts. Using a "Bayesian Block" method to identify significantly distinct pulse peaks, we find an order of magnitude fewer pulses than found in studies of long bursts. The disparity in lag magnitude is discontinuous across the ~ 2-s valley between long and short bursts. Thus, short bursts do not appear to be representable as a continuation of long bursts' temporal characteristics.

  4. Gravitational Radiation from Gamma-Ray Bursts

    E-Print Network [OSTI]

    Tsvi Piran

    2001-02-19T23:59:59.000Z

    Gamma Ray Bursts (GRBs) are the most relativistic objects known so far, involving, on one hand an ultra-relativistic motion with a Lorentz factor $\\Gamma > 100$ and on the other hand an accreting newborn black hole. The two main routes leading to this scenario: binary neutron star mergers and Collapsar - the collapse of a rotating star to a black hole, are classical sources for gravitational radiation. Additionally one expect a specific a gravitational radiation pulse associated with the acceleration of the relativistic ejecta. I consider here the implication of the observed rates of GRBs to the possibility of detection of a gravitational radiation signal associated with a GRB. Unfortunately I find that, with currently planned detectors it is impossible to detect the direct gravitational radiation associated with the GRB. It is also quite unlikely to detect gravitational radiation associated with Collapsars. However, the detection of gravitational radiation from a neutron star merger associated with a GRB is likely.

  5. Super Luminous Supernova and Gamma Ray Bursts

    E-Print Network [OSTI]

    Shlomo Dado; Arnon Dar

    2012-11-08T23:59:59.000Z

    We use a simple analytical model to derive a closed form expression for the bolometric light-curve of super-luminus supernovae (SLSNe) powered by a plastic collision between the fast ejecta from core collapse supernovae (SNe) of types Ib/c and IIn and slower massive circum-stellar shells, ejected during the late stage of the life of their progenitor stars preceding the SN explosion. We demonstrate that this expression reproduces well the bolometric luminosity of SLSNe with and without an observed gamma ray burst (GRB), and requires only a modest amount ($M < 0.1\\,M_\\odot$) of radioactive $^{56}$Ni synthesized in the SN explosion in order to explain their late-time luminosity. Long duration GRBs can be produced by ordinary SNe of type Ic rather than by 'hypernovae' - a subclass of superenergetic SNeIb/c.

  6. Search for Gamma Ray Bursts at Chacaltaya

    E-Print Network [OSTI]

    Silvia Vernetto; for the INCA Collaboration

    2000-11-13T23:59:59.000Z

    A search for Gamma Ray Bursts in the GeV-TeV energy range has been performed by INCA, an air shower array working at 5200 m of altitude at the Chacaltaya Laboratory (Bolivia). The altitude of the detector and the use of the "single particle technique" allows to lower the energy threshold up to few GeVs. No significant signals are observed during the occurrence of 125 GRBs detected by BATSE, and the obtained upper limits on the energy fluence in the interval 1-1000(100) GeV range from 3.2(8.6) 10^-5 to 2.6(7.0) 10^-2 erg/cm^2 depending on the zenith angle of the events. These limits, thanks to the extreme altitude of INCA, are the lowest ever obtained in the sub-TeV energy region by a ground based esperiment.

  7. Compton Recoil Electron Tracking With the TIGRE Gamma-Ray Balloon Experiment

    E-Print Network [OSTI]

    Kamiya, Kaoru

    2011-01-01T23:59:59.000Z

    AGNs), pulsars, gamma-ray bursts, cosmic ray interactionssensitive to cosmic gamma-ray bursts in the energy range ofGalactic center, a single gamma-ray burst which occurred 10

  8. The Search for Muon Neutrinos from Northern Hemisphere Gamma-Ray Bursts with AMANDA

    E-Print Network [OSTI]

    Achterberg, A.; IceCube Collaboration

    2008-01-01T23:59:59.000Z

    see also the Swift Gamma-Ray Burst Mission Page: http://from Northern Hemisphere Gamma-Ray Bursts with AMANDA A.Northern Hemisphere Gamma-Ray Bursts with AMANDA The IceCube

  9. Search for muon neutrinos from Gamma-Ray Bursts with the IceCube neutrino telescope

    E-Print Network [OSTI]

    Abbasi, R.

    2010-01-01T23:59:59.000Z

    2009, GCN: The Gamma ray bursts Coordinates Network, http://for muon neutrinos from Gamma-Ray Bursts with the IceCubeMereghetti, S. 2004, in Gamma-ray Bursts: 30 Years of

  10. Long gamma-ray bursts and core-collapse supernovae have different environments

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    Progenitor Stars of Gamma-Ray Bursts. Astrophys. J. 637, 45.massive stars towards gamma-ray bursts. Astr. Astrophys.On the Lyalpha emission from gamma-ray burst host galaxies:

  11. GRB 020410: A Gamma-ray burst afterglow discovered by its supernova light

    E-Print Network [OSTI]

    2004-01-01T23:59:59.000Z

    Training Network “Gamma-Ray Bursts: An Enigma and a Tool”,Journal GRB 020410: A Gamma-Ray Burst Afterglow DiscoveredSubject headings: gamma rays: bursts – supernova: general

  12. MAGNETIC STRUCTURES IN GAMMA-RAY BURST JETS PROBED BY GAMMA-RAY POLARIZATION

    SciTech Connect (OSTI)

    Yonetoku, Daisuke; Murakami, Toshio; Morihara, Yoshiyuki; Takahashi, Takuya; Wakashima, Yudai; Yonemochi, Hajime; Sakashita, Tomonori; Fujimoto, Hirofumi; Kodama, Yoshiki [College of Science and Engineering, School of Mathematics and Physics, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192 (Japan); Gunji, Shuichi; Toukairin, Noriyuki [Department of Physics, Faculty of Science, Yamagata University, 1-4-12, Koshirakawa, Yamagata, Yamagata 990-8560 (Japan); Mihara, Tatehiro [Cosmic Radiation Laboratory, RIKEN, 2-1, Hirosawa, Wako City, Saitama 351-0198 (Japan); Toma, Kenji, E-mail: yonetoku@astro.s.kanazawa-u.ac.jp [Department of Earth and Space Science, Osaka University, Toyonaka 560-0043 (Japan)

    2012-10-10T23:59:59.000Z

    We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB 110301A and GRB 110721A, observed with the gamma-ray burst polarimeter (GAP) on borad the IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of {Pi} = 70 {+-} 22% with statistical significance of 3.7{sigma} for GRB 110301A, and {Pi} = 84{sup +16}{sub -28}% with 3.3{sigma} confidence level for GRB 110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB 100826A, which showed a significant change of polarization angle, as reported in Yonetoku et al. Synchrotron emission model can be consistent with the data of the three GRBs, while the photospheric quasi-thermal emission model is not favored. We suggest that magnetic field structures in the emission region are globally ordered fields advected from the central engine.

  13. Magnetic Structures in Gamma-Ray Burst Jets Probed by Gamma-Ray Polarization

    E-Print Network [OSTI]

    Daisuke Yonetoku; Toshio Murakami; Shuichi Gunji; Tatehiro Mihara; Kenji Toma; Yoshiyuki Morihara; Takuya Takahashi; Yudai Wakashima; Hajime Yonemochi; Tomonori Sakashita; Noriyuki Toukairin; Hirofumi Fujimoto; Yoshiki Kodama

    2012-08-27T23:59:59.000Z

    We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB 110301A and GRB 110721A, observed with the Gamma-ray burst polarimeter (GAP) aboard IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of $\\Pi = 70 \\pm 22$% with statistical significance of $3.7 \\sigma$ for GRB 110301A, and $\\Pi = 84^{+16}_{-28}$% with $3.3 \\sigma$ confidence level for GRB 110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB 100826A, which showed a significant change of polarization angle, as reported in Yonetoku et al. (2011). Synchrotron emission model can be consistent with all the data of the three GRBs, while photospheric quasi-thermal emission model is not favorable. We suggest that magnetic field structures in the emission region are globally-ordered fields advected from the central engine.

  14. Gravitational waves versus X-ray and gamma-ray emission in a short gamma-ray burst

    SciTech Connect (OSTI)

    Oliveira, F. G.; Rueda, Jorge A.; Ruffini, R., E-mail: fe.fisica@gmail.com, E-mail: jorge.rueda@icra.it, E-mail: ruffini@icra.it [Dipartimento di Fisica and ICRA, Sapienza Universitŕ di Roma, P.le Aldo Moro 5, I-00185 Rome (Italy)

    2014-06-01T23:59:59.000Z

    Recent progress in the understanding of the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst (GRB), GRB 090227B, allows us to give an estimate of the gravitational waves versus the X-ray and gamma-ray emission in a short GRB.

  15. High Energy Gamma-Ray Emission from Gamma-Ray Bursts - Before GLAST

    SciTech Connect (OSTI)

    Fan, Yi-Zhong; Piran, Tsvi

    2011-11-29T23:59:59.000Z

    Gamma-ray bursts (GRBs) are short and intense emission of soft {gamma}-rays, which have fascinated astronomers and astrophysicists since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the cosmological origin of GRBs, support the fireball model, and imply a long-activity of the central engine. The high-energy {gamma}-ray emission (> 20 MeV) from GRBs is particularly important because they shed some lights on the radiation mechanisms and can help us to constrain the physical processes giving rise to the early afterglows. In this work, we review observational and theoretical studies of the high-energy emission from GRBs. Special attention is given to the expected high-energy emission signatures accompanying the canonical early-time X-ray afterglow that was observed by the Swift X-ray Telescope. We also discuss the detection prospect of the upcoming GLAST satellite and the current ground-based Cerenkov detectors.

  16. Constraints on Very High Energy gamma-ray emission from Gamma-Ray Bursts

    E-Print Network [OSTI]

    Atkins, R; Berley, D; Blaufuss, E; Coyne, D G; De Young, T R; Dingus, B L; Dorfan, D E; Ellsworth, R W; Fleysher, L; Fleysher, R; González, M M; Goodman, J A; Hays, E; Hoffman, C M; Kelley, L A; Lansdell, C P; Linnemann, J T; McEnery, J E; Mincer, A I; Morales, M F; Némethy, P; Noyes, D; Ryan, J M; Samuelson, F W; Parkinson, P M S; Shoup, A; Sinnis, G; Smith, A J; Sullivan, G W; Williams, D A; Wilson, M E; Xu, X W; Yodh, G B

    2005-01-01T23:59:59.000Z

    The Milagro gamma-ray observatory employs a water Cherenkov detector to observe extensive air showers produced by high energy particles interacting in the Earth's atmosphere. Milagro has a wide field of view and high duty cycle, monitoring the northern sky almost continuously in the 100 GeV to 100 TeV energy range. Milagro is, thus, uniquely capable of searching for very high-energy emission from gamma-ray bursts (GRBs) during the prompt emission phase. Detection of >100 GeV counterparts would place powerful constraints on GRB mechanisms. Twenty-five satellite-triggered GRBs occurred within the field of view of Milagro between January 2000 and December 2001. We have searched for counterparts to these GRBs and found no significant emission from any of the burst positions. Due to the absorption of high-energy gamma rays by the extragalactic background light, detections are only expected to be possible for redshifts less than ~0.5. Three of the GRBs studied have measured redshifts. GRB 010921 has a redshift low ...

  17. Constraints on Very High Energy gamma-ray emission from Gamma-Ray Bursts

    E-Print Network [OSTI]

    R. Atkins; W. Benbow; D. Berley; E. Blaufuss; D. G. Coyne; T. DeYoung; B. L. Dingus; D. E. Dorfan; R. W. Ellsworth; L. Fleysher; R. Fleysher; M. M. Gonzalez; J. A. Goodman; E. Hays; C. M. Hoffman; L. A. Kelley; C. P. Lansdell; J. T. Linnemann; J. E. McEnery; A. I. Mincer; M. F. Morales; P. Nemethy; D. Noyes; J. M. Ryan; F. W. Samuelson; P. M. Saz Parkinson; A. Shoup; G. Sinnis; A. J. Smith; G. W. Sullivan; D. A. Williams; M. E. Wilson; X. W. Xu; G. B. Yodh

    2005-03-11T23:59:59.000Z

    The Milagro gamma-ray observatory employs a water Cherenkov detector to observe extensive air showers produced by high energy particles interacting in the Earth's atmosphere. Milagro has a wide field of view and high duty cycle, monitoring the northern sky almost continuously in the 100 GeV to 100 TeV energy range. Milagro is, thus, uniquely capable of searching for very high-energy emission from gamma-ray bursts (GRBs) during the prompt emission phase. Detection of >100 GeV counterparts would place powerful constraints on GRB mechanisms. Twenty-five satellite-triggered GRBs occurred within the field of view of Milagro between January 2000 and December 2001. We have searched for counterparts to these GRBs and found no significant emission from any of the burst positions. Due to the absorption of high-energy gamma rays by the extragalactic background light, detections are only expected to be possible for redshifts less than ~0.5. Three of the GRBs studied have measured redshifts. GRB 010921 has a redshift low enough (0.45) to allow an upper limit on the fluence to place an observational constraint on potential GRB models.

  18. A Blind Search for Bursts of Very High Enery Gamma Rays with Milagro

    E-Print Network [OSTI]

    Vlasios Vasileiou

    2008-11-10T23:59:59.000Z

    Milagro is a water-Cherenkov detector that observes the extended air showers produced by cosmic gamma rays of energies E>100GeV. The effective area of Milagro peaks at energies E~10TeV, however it is still large even down to a few hundred GeV (~10m^2 at 100GeV). The wide field of view (~2sr) and high duty cycle (>90%) of Milagro make it ideal for continuously monitoring the overhead sky for transient Very High Energy (VHE) emissions. This study searched the Milagro data for such emissions. Even though the search was optimized primarily for detecting the emission from Gamma-Ray Bursts (GRBs), it was still sensitive to the emission from the last stages of the evaporation of Primordial Black Holes or to any other kind of phenomena that produce bursts of VHE gamma rays. Measurements of the GRB spectra by satellites up to few tens of GeV showed no signs of a cutoff. Even though multiple instruments sensitive to $GeV/TeV$ gamma rays have performed observations of GRBs, there has not yet been a definitive detection of such an emission yet. One of the reasons for that is that gamma rays with energies E>~100GeV are attenuated by interactions with the extragalactic background light or are absorbed internally at the site of the burst. There are many models that predict VHE gamma-ray emission from GRBs. A detection or a constraint of such an emission can provide useful information on the mechanism and environment of GRBs. This study performed a blind search of the Milagro data of the last five years for bursts of VHE gamma rays with durations ranging from 100musec to 316sec. No GRB localization was provided by an external instrument. Instead, the whole dataset was thoroughly searched in time, space, and duration. No significant events were detected. Upper limits were placed on the VHE emission from GRBs.

  19. Fundamental Physics from the Sky: Cosmic Rays, Gamma Rays and the Hunt for Dark Matter

    E-Print Network [OSTI]

    Profumo, Stefano

    2012-01-01T23:59:59.000Z

    Can we learn about New Physics with astronomical and astro-particle data? Understanding how this is possible is key to unraveling one of the most pressing mysteries at the interface of cosmology and particle physics: the fundamental nature of dark matter. I will discuss some of the recent puzzling findings in cosmic-ray electron-positron data and in gamma-ray observations that might be related to dark matter. I will argue that recent cosmic-ray data, most notably from the Pamela and Fermi satellites, indicate that previously unaccounted-for powerful sources in the Galaxy inject high-energy electrons and positrons. Interestingly, this new source class might be related to new fundamental particle physics, and specifically to pair-annihilation or decay of galactic dark matter. This exciting scenario is directly constrained by Fermi gamma-ray observations, which also inform us on astrophysical source counterparts that could also be responsible for the high-energy electron-positron excess. Observations of gamma-ra...

  20. Evidence for Gamma-ray Emission from the Newly Discovered Dwarf Galaxy Reticulum 2

    E-Print Network [OSTI]

    Geringer-Sameth, Alex; Koushiappas, Savvas M; Koposov, Sergey E; Belokurov, Vasily; Torrealba, Gabriel; Evans, N Wyn

    2015-01-01T23:59:59.000Z

    We present a search for gamma-ray emission from the direction of the newly discovered dwarf galaxy Reticulum 2. Using Fermi-LAT data, we detect a signal that exceeds expected backgrounds between ~2-10 GeV and is consistent with annihilation of dark matter for particle masses less than a few x 10^2 GeV. Modeling the background as a Poisson process based on Fermi-LAT diffuse models, and taking into account trials factors, we detect emission with p-value less than 9.8 x 10^-5 (>3.7 sigma). An alternative, model-independent treatment of background reduces the significance, raising the p-value to 9.7 x 10^-3 (2.3 sigma). Even in this case, however, Reticulum 2 has the most significant gamma-ray signal of any known dwarf galaxy. If Reticulum 2 has a dark matter halo that is similar to those inferred for other nearby dwarfs, the signal is consistent with the s-wave relic abundance cross section for annihilation.

  1. On the sensitivity of the HAWC observatory to gamma-ray bursts

    E-Print Network [OSTI]

    Abeysekara, A U; Aguilar, S; Alfaro, R; Almaraz, E; Álvarez, C; Álvarez-Romero, J de D; Álvarez, M; Arceo, R; Arteaga-Velázquez, J C; Badillo, C; Barber, A; Baughman, B M; Bautista-Elivar, N; Belmont, E; Benítez, E; BenZvi, S Y; Berley, D; Bernal, A; Bonamente, E; Braun, J; Caballero-Lopez, R; Cabrera, I; Carramińana, A; Carrasco, L; Castillo, M; Chambers, L; Conde, R; Condreay, P; Cotti, U; Cotzomi, J; D'Olivo, J C; de la Fuente, E; De León, C; Delay, S; Delepine, D; DeYoung, T; Diaz, L; Diaz-Cruz, L; Dingus, B L; Duvernois, M A; Edmunds, D; Ellsworth, R W; Fick, B; Fiorino, D W; Flandes, A; Fraija, N I; Galindo, A; García-Luna, J L; García-Torales, G; Garfias, F; González, L X; González, M M; Goodman, J A; Grabski, V; Gussert, M; Guzmán-Ceron, C; Hampel-Arias, Z; Harris, T; Hays, E; Hernandez-Cervantes, L; Hüntemeyer, P H; Imran, A; Iriarte, A; Jimenez, J J; Karn, P; Kelley-Hoskins, N; Kieda, D; Langarica, R; Lara, A; Lauer, R; Lee, W H; Linares, E C; Linnemann, J T; Longo, M; Luna-García, R; Martínez, H; Martínez, J; Martínez, L A; Martínez, O; Martínez-Castro, J; Martos, M; Matthews, J; McEnery, J E; Medina-Tanco, G; Mendoza-Torres, J E; Miranda-Romagnoli, P A; Montaruli, T; Moreno, E; Mostafa, M; Napsuciale, M; Nava, J; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T; Tapia, A Olmos; Orozco, V; Pérez, V; Pérez-Pérez, E G; Perkins, J S; Pretz, J; Ramirez, C; Ramírez, I; Rebello, D; Rentería, A; Reyes, J; Rosa-González, D; Rosado, A; Ryan, J M; Sacahui, J R; Salazar, H; Salesa, F; Sandoval, A; Santos, E; Schneider, M; Shoup, A; Silich, S; Sinnis, G; Smith, A J; Sparks, K; Springer, W; Suárez, F; Suarez, N; Taboada, I; Tellez, A F; Tenorio-Tagle, G; Tepe, A; Toale, P A; Tollefson, K; Torres, I; Ukwatta, T N; Valdes-Galicia, J; Vanegas, P; Vasileiou, V; Vázquez, O; Vázquez, X; Villaseńor, L; Wall, W; Walters, J S; Warner, D; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Zaborov, D; Zepeda, A

    2011-01-01T23:59:59.000Z

    We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100 m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will prov...

  2. Gamma Ray Burst Constraints on Ultraviolet Lorentz Invariance Violation

    E-Print Network [OSTI]

    Tina Kahniashvili; Grigol Gogoberidze; Bharat Ratra

    2006-10-20T23:59:59.000Z

    We present a unified general formalism for ultraviolet Lorentz invariance violation (LV) testing through electromagnetic wave propagation, based on both dispersion and rotation measure data. This allows for a direct comparison of the efficacy of different data to constrain LV. As an example we study the signature of LV on the rotation of the polarization plane of $\\gamma$-rays from gamma ray bursts in a LV model. Here $\\gamma$-ray polarization data can provide a strong constraint on LV, 13 orders of magnitude more restrictive than a potential constraint from the rotation of the cosmic microwave background polarization proposed by Gamboa, L\\'{o}pez-Sarri\\'{o}n, and Polychronakos (2006).

  3. Gamma-ray electrification of a dielectric

    SciTech Connect (OSTI)

    Arkhipov, V.I.; Gromov, V.V.; Mamonov, M.N.; Rozno, A.G.; Rudenko, A.I.; Strikhanov, M.N.

    1987-08-01T23:59:59.000Z

    In this work the behavior of the characteristics of the volume charge induced by a ..gamma..-ray pulse in a thick plane-parallel plate, under the normal incidence of a beam of monoenergetic quanta ranging from 10 keV to 1 MeV, is examined. The theoretical results obtained are compared with experimental data obtained for a layer of polymethyl methacrylate 1.8 mm thick with the use of the spectrum of x-ray bremmstrahlung, produced by 1 MeV electrons passing through an iron target with a specific thickness of 0.796 g/cm/sup 2/. The density distribution of the volume charge was obtained taking into account in detail the angular characteristics of the photo- and Compton electrons. A simple procedure was used to take into account the effect of multiple scattering of the electrons; unlike well-known computational methods it enabled clear physical interpretation and did not require large amounts of computer time in carrying out the calculations.

  4. Diffuse Gamma-Ray Emission from Large Scale Structures

    E-Print Network [OSTI]

    Dobardzic, Aleksandra

    2012-01-01T23:59:59.000Z

    For more than a decade now the complete origin of the diffuse gamma-ray emission background (EGRB) has been unknown. Major components like unresolved star-forming galaxies (making 10GeV. Moreover, we show that, even though the gamma-ray emission arising from structure formation shocks at galaxy clusters is below previous estimates, these large scale shocks can still give an important, and even dominant at high energies, contribution to the EGRB. Future detections of cluster gamma-ray emission would make our upper limit of the extragalactic gamma-ray emission from structure-formation process, a firm prediction, and give us deeper insight in evolution of these large scale shock.

  5. INTERPLANETARY NETWORK LOCALIZATIONS OF KONUS SHORT GAMMA-RAY BURSTS

    E-Print Network [OSTI]

    Vanderspek, Roland K.

    Between the launch of the Global Geospace Science Wind spacecraft in 1994 November and the end of 2010, the Konus-Wind experiment detected 296 short-duration gamma-ray bursts (including 23 bursts which can be classified ...

  6. Redshifts of the Long Gamma-Ray Bursts

    E-Print Network [OSTI]

    Z. Bagoly; I. Csabai; A. Meszaros; P. Meszaros; I. Horvath; L. G. Balazs; R. Vavrek

    2007-04-06T23:59:59.000Z

    The low energy spectra of some gamma-ray bursts' show excess components beside the power-law dependence. The consequences of such a feature allows to estimate the gamma photometric redshift of the long gamma-ray bursts in the BATSE Catalog. There is good correlation between the measured optical and the estimated gamma photometric redshifts. The estimated redshift values for the long bright gamma-ray bursts are up to z=4, while for the the faint long bursts - which should be up to z=20 - the redshifts cannot be determined unambiguously with this method. The redshift distribution of all the gamma-ray bursts with known optical redshift agrees quite well with the BATSE based gamma photometric redshift distribution.

  7. A Gamma-Ray Burst Bibliography, 1973-1999

    E-Print Network [OSTI]

    K. Hurley

    1999-12-02T23:59:59.000Z

    On the average, one new publication on cosmic gamma-ray bursts enters the literature every day. The total number now exceeds 4100. I present here a complete bibliography which can be made available electronically to interested parties.

  8. Robust Limits on Lorentz Violation from Gamma-Ray Bursts

    E-Print Network [OSTI]

    John Ellis; Nick E. Mavromatos; Dimitri V. Nanopoulos; Alexander S. Sakharov; Edward K. G. Sarkisyan

    2005-10-06T23:59:59.000Z

    We constrain the possibility of a non-trivial refractive index in free space corresponding to an energy-dependent velocity of light: c(E) \\simeq c_0 (1 - E/M), where M is a mass scale that might represent effect of quantum-gravitational space-time foam, using the arrival times of sharp features observed in the intensities of radiation with different energies from a large sample of gamma-ray bursters (GRBs) with known redshifts. We use wavelet techniques to identify genuine features, which we confirm in simulations with artificial added noise. Using the weighted averages of the time-lags calculated using correlated features in all the GRB light curves, we find a systematic tendency for more energetic photons to arrive earlier. However, there is a very strong correlation between the parameters characterizing an intrinsic time-lag at the source and a distance-dependent propagation effect. Moreover, the significance of the earlier arrival times is less evident for a subsample of more robust spectral structures. Allowing for intrinsic stochastic time-lags in these features, we establish a statistically robust lower limit: M > 0.9x10^{16} GeV on the scale of violation of Lorentz invariance.

  9. Particle Swarm Imaging (PSIM) - Innovative Gamma-Ray Assay - 13497

    SciTech Connect (OSTI)

    Parvin, Daniel; Clarke, Sean; Humes, Sarah J. [Babcock International Group, Sellafield, Cumbria (United Kingdom)] [Babcock International Group, Sellafield, Cumbria (United Kingdom)

    2013-07-01T23:59:59.000Z

    Particle Swarm Imaging is an innovative technique used to perform quantitative gamma-ray assay. The innovation overcomes some of the difficulties associated with the accurate measurement and declaration of measurement uncertainties of radionuclide inventories within waste items when the distribution of activity is unknown. Implementation requires minimal equipment, with field measurements and results obtained using only a single electrically cooled HRGS gamma-ray detector. Examples of its application in the field are given in this paper. (authors)

  10. Gamma-ray tracking method for pet systems

    DOE Patents [OSTI]

    Mihailescu, Lucian; Vetter, Kai M.

    2010-06-08T23:59:59.000Z

    Gamma-ray tracking methods for use with granular, position sensitive detectors identify the sequence of the interactions taking place in the detector and, hence, the position of the first interaction. The improved position resolution in finding the first interaction in the detection system determines a better definition of the direction of the gamma-ray photon, and hence, a superior source image resolution. A PET system using such a method will have increased efficiency and position resolution.

  11. Hyperstars - Main Origin of Short Gamma Ray Bursts?

    E-Print Network [OSTI]

    Arnon Dar

    2005-09-09T23:59:59.000Z

    The first well-localized short-duration gamma ray bursts (GRBs), GRB 050509b, GRB 050709 and GRB 050724, could have been the narrowly beamed initial spike of a burst/hyper flare of soft gamma ray repeaters (SGRs) in host galaxies at cosmological distances. Such bursts are expected if SGRs are young hyperstars, i.e. neutron stars where a considerable fraction of their neutrons have converted to hyperons and/or strange quark matter.

  12. Gamma Ray Bursts as Probes of Quantum Gravity

    E-Print Network [OSTI]

    Tsvi Piran

    2004-07-21T23:59:59.000Z

    Gamma ray bursts (GRBs) are short and intense pulses of $\\gamma$-rays arriving from random directions in the sky. Several years ago Amelino-Camelia et al. pointed out that a comparison of time of arrival of photons at different energies from a GRB could be used to measure (or obtain a limit on) possible deviations from a constant speed of light at high photons energies. I review here our current understanding of GRBs and reconsider the possibility of performing these observations.

  13. Relativity at Action or Gamma-Ray Bursts

    E-Print Network [OSTI]

    Tsvi Piran

    1996-07-08T23:59:59.000Z

    Gamma ray Bursts (GRBs) - short bursts of few hundred keV $\\gamma$-rays - have fascinated astronomers since their accidental discovery in the sixties. GRBs were ignored by most relativists who did not expect that they are associated with any relativistic phenomenon. The recent observations of the BATSE detector on the Compton GRO satellite have revolutionized our ideas on these bursts and the picture that emerges shows that GRBs are the most relativistic objects discovered so far.

  14. Science with the new generation high energy gamma- ray experiments

    E-Print Network [OSTI]

    M. Alvarez; D. D'Armiento; G. Agnetta; A. Alberdi; A. Antonelli; A. Argan; P. Assis; E. A. Baltz; C. Bambi; G. Barbiellini; H. Bartko; M. Basset; D. Bastieri; P. Belli; G. Benford; L. Bergstrom; R. Bernabei; G. Bertone; A. Biland; B. Biondo; F. Bocchino; E. Branchini; M. Brigida; T. Bringmann; P. Brogueira; A. Bulgarelli; J. A. Caballero; G. A. Caliandro; P. Camarri; F. Cappella; P. Caraveo; R. Carbone; M. Carvajal; S. Casanova; A. J. Castro-Tirado; O. Catalano; R. Catena; F. Celi; A. Celotti; R. Cerulli; A. Chen; R. Clay; V. Cocco; J. Conrad; E. Costa; A. Cuoco; G. Cusumano; C. J. Dai; B. Dawson; B. De Lotto; G. De Paris; A. de Ugarte Postigo; E. Del Monte; C. Delgado; A. Di Ciaccio; G. Di Cocco; S. Di Falco; G. Di Persio; B. L. Dingus; A. Dominguez; F. Donato; I. Donnarumma; M. Doro; J. Edsjo; J. M. Espino Navas; M. C. Espirito Santo; Y. Evangelista; C. Evoli; D. Fargion; C. Favuzzi; M. Feroci; M. Fiorini; L. Foggetta; N. Fornengo; T. Froysland; M. Frutti; F. Fuschino; J. L. Gomez; M. Gomez; D. Gaggero; N. Galante; M. I. Gallardo; M. Galli; J. E. Garcia; M. Garczarczyk; F. Gargano; M. Gaug; F. Gianotti; S. Giarrusso; B. Giebels; N. Giglietto; P. Giommi; F. Giordano; A. Giuliani; J. Glicenstein; P. Goncalves; D. Grasso; M. Guerriero; H. L. He; A. Incicchitti; J. Kirk; H. H. Kuang; A. La Barbera; G. La Rosa; C. Labanti; G. Lamanna; I. Lapshov; F. Lazzarotto; S. Liberati; F. Liello; P. Lipari; F. Longo; F. Loparco; M. Lozano; P. G. Lucentini De Sanctis; J. M. Ma; M. C. Maccarone; L. Maccione; V. Malvezzi; A. Mangano; M. Mariotti; M. Marisaldi; I. Martel; A. Masiero; E. Massaro; M. Mastropietro; E. Mattaini; F. Mauri; M. N. Mazziotta; S. Mereghetti; T. Mineo; S. Mizobuchi; A. Moiseev; M. Moles; C. Monte; F. Montecchia; E. Morelli; A. Morselli; I. Moskalenko; F. Nozzoli; J. F. Ormes; M. A. Peres-Torres; L. Pacciani; A. Pellizzoni; F. Perez-Bernal; F. Perotti; P. Picozza; L. Pieri; M. Pietroni; M. Pimenta; A. Pina; C. Pittori; C. Pontoni; G. Porrovecchio; F. Prada; M. Prest; D. Prosperi; R. Protheroe; G. Pucella; J. M. Quesada; J. M. Quintana; J. R. Quintero; S. Raino; M. Rapisarda; M. Rissi; J. Rodriguez; E. Rossi; G. Rowell; A. Rubini; F. Russo; M. Sanchez-Conde; B. Sacco; V. Scapin; M. Schelke; A. Segreto; A. Sellerholm; X. D. Sheng; A. Smith; P. Soffitta; R. Sparvoli; P. Spinelli; V. Stamatescu; L. S. Stark; M. Tavani; G. Thornton; L. G. Titarchuk; B. Tome; A. Traci; M. Trifoglio; A. Trois; P. Vallania; E. Vallazza; S. Vercellone; S. Vernetto; V. Vitale; N. Wild; Z. P. Ye; A. Zambra; F. Zandanel; D. Zanello

    2007-12-04T23:59:59.000Z

    This Conference is the fifth of a series of Workshops on High Energy Gamma- ray Experiments, following the Conferences held in Perugia 2003, Bari 2004, Cividale del Friuli 2005, Elba Island 2006. This year the focus was on the use of gamma-ray to study the Dark Matter component of the Universe, the origin and propagation of Cosmic Rays, Extra Large Spatial Dimensions and Tests of Lorentz Invariance.

  15. Science with the new generation high energy gamma- ray experiments

    E-Print Network [OSTI]

    Alvarez, M; Agnetta, G; Alberdi, A; Antonelli, A; Argan, A; Assis, P; Baltz, E A; Bambi, C; Barbiellini, G; Bartko, H; Basset, M; Bastieri, D; Belli, P; Benford, G; Bergström, L; Bernabei, R; Bertone, G; Biland, A; Biondo, B; Bocchino, F; Branchini, E; Brigida, M; Bringmann, T; Brogueira, P; Bulgarelli, A; Caballero, J A; Caliandro, G A; Camarri, P; Cappella, F; Caraveo, P; Carbone, R; Carvajal, M; Casanova, S; Castro-Tirado, A J; Catalano, O; Catena, R; Celi, F; Celotti, A; Cerulli, R; Chen, A; Clay, R; Cocco, V; Conrad, J; Costa, E; Cuoco, A; Cusumano, G; Dai, C J; Dawson, B; De Lotto, B; De Paris, G; Postigo, A de Ugarte; Del Monte, E; Delgado, C; Di Ciaccio, A; Di Cocco, G; Di Falco, S; Di Persio, G; Dingus, B L; Dominguez, A; Donato, F; Donnarumma, I; Doro, M; Edsjö, J; Navas, J M Espino; Santo, M C Espirito; Evangelista, Y; Evoli, C; Fargion, D; Favuzzi, C; Feroci, M; Fiorini, M; Foggetta, L; Fornengo, N; Froysland, T; Frutti, M; Fuschino, F; Gómez, J L; Gómez, M; Gaggero, D; Galante, N; Gallardo, M I; Galli, M; García, J E; Garczarczyk, M; Gargano, F; Gaug, M; Gianotti, F; Giarrusso, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Giuliani, A; Glicenstein, J; Gonçalves, P; Grasso, D; Guerriero, M; He, H L; Incicchitti, A; Kirk, J; Kuang, H H; La Barbera, A; La Rosa, G; Labanti, C; Lamanna, G; Lapshov, I; Lazzarotto, F; Liberati, S; Liello, F; Lipari, P; Longo, F; Loparco, F; Lozano, M; De Sanctis, P G Lucentini; Ma, J M; Maccarone, M C; Maccione, L; Malvezzi, V; Mangano, A; Mariotti, M; Marisaldi, M; Martel, I; Masiero, A; Massaro, E; Mastropietro, M; Mattaini, E; Mauri, F; Mazziotta, M N; Mereghetti, S; Mineo, T; Mizobuchi, S; Moiseev, A; Moles, M; Monte, C; Montecchia, F; Morelli, E; Morselli, A; Moskalenko, I; Nozzoli, F; Ormes, J F; Peres-Torres, M A; Pacciani, L; Pellizzoni, A; Pérez-Bernal, F; Perotti, F; Picozza, P; Pieri, L; Pietroni, M; Pimenta, M; Pina, A; Pittori, C; Pontoni, C; Porrovecchio, G; Prada, F; Prest, M; Prosperi, D; Protheroe, R; Pucella, G; Quesada, J M; Quintana, J M; Quintero, J R; Rainó, S; Rapisarda, M; Rissi, M; Rodríguez, J; Rossi, E; Rowell, G; Rubini, A; Russo, F; Sanchez-Conde, M; Sacco, B; Scapin, V; Schelke, M; Segreto, A; Sellerholm, A; Sheng, X D; Smith, A; Soffitta, P; Sparvoli, R; Spinelli, P; Stamatescu, V; Stark, L S; Tavani, M; Thornton, G; Titarchuk, L G; Tomé, B; Traci, A; Trifoglio, M; Trois, A; Vallania, P; Vallazza, E; Vercellone, S; Vernetto, S; Vitale, V; Wild, N; Ye, Z P; Zambra, A; Zandanel, F; Zanello, D

    2007-01-01T23:59:59.000Z

    This Conference is the fifth of a series of Workshops on High Energy Gamma- ray Experiments, following the Conferences held in Perugia 2003, Bari 2004, Cividale del Friuli 2005, Elba Island 2006. This year the focus was on the use of gamma-ray to study the Dark Matter component of the Universe, the origin and propagation of Cosmic Rays, Extra Large Spatial Dimensions and Tests of Lorentz Invariance.

  16. MILAGRO CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM SHORT-DURATION GAMMA-RAY BURSTS

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    MILAGRO CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM SHORT-DURATION GAMMA-RAY BURSTS A. A. Abdo,1 localizations of short, hard gamma-ray bursts (GRBs) by the Swift and HETE satellites have led: bursts -- gamma rays: observations Gamma-ray bursts (GRBs) have long been classified by their durations

  17. CORRELATIONS OF PROMPT AND AFTERGLOW EMISSION IN SWIFT LONG AND SHORT GAMMA-RAY BURSTS

    E-Print Network [OSTI]

    Zhang, Bing

    CORRELATIONS OF PROMPT AND AFTERGLOW EMISSION IN SWIFT LONG AND SHORT GAMMA-RAY BURSTS N. Gehrels,1 of prompt and afterglow emission from gamma-ray bursts (GRBs) between different spectral bands have been-limited for long events. Subject headingg: gamma rays: bursts 1. INTRODUCTION One of the longest enduring gamma-ray

  18. Ivan De Mitri VHE Gamma Ray Astronomy 1 Very High Energy

    E-Print Network [OSTI]

    Harrison, Thomas

    ~ 1/day Gamma Ray Bursts The X-ray counterpart detection with better pointing accuracy instrumentsIvan De Mitri VHE Gamma Ray Astronomy 1 Very High Energy Gamma Ray Astronomy Ivan De Mitri'Aquila, 11- Jun -2002 Photo F. Arneodo #12;Ivan De Mitri VHE Gamma Ray Astronomy 2 Seminar Outline Background

  19. Radio emissions from terrestrial gamma-ray flashes Joseph R. Dwyer1

    E-Print Network [OSTI]

    Cummer, Steven A.

    . Introduction 1.1. TGF Theory Overview [2] Terrestrial gamma-ray flashes (TGFs) are bright bursts of gamma raysRadio emissions from terrestrial gamma-ray flashes Joseph R. Dwyer1 and Steven A. Cummer2 Received frequency (RF) emissions by terrestrial gamma-ray flashes (TGFs) is developed. These radio emissions, which

  20. PoGO : The Polarised Gamma-ray Observer S. Larssona

    E-Print Network [OSTI]

    Haviland, David

    . Recently, the detection of high linear polarisation, (80±20)%, in a gamma ray burst ob- served, this observation will have far reaching implications for models of gamma- ray bursts. Many of the X-ray and gamma-ray1 PoGO : The Polarised Gamma-ray Observer S. Larssona and M. Pearceb (for the PoGO Collaboration

  1. Proceedings of ICRC 2001: 1 c Copernicus Gesellschaft 2001 Status of the Milagro Gamma Ray Observatory

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    , active galactic nuclei (AGN), and gamma ray bursts (GRB). In addition, more exotic sources like Gamma Ray Observatory, located at an altitude of 8,600 feet in the Jemez Mountains of New Mexico for sources of TeV gamma rays. It is uniquely capable of search- ing for transient sources of VHE gamma rays

  2. Measurements and implications of the relationship between lightning and terrestrial gamma ray flashes

    E-Print Network [OSTI]

    Cummer, Steven A.

    the discovery of short bursts of gamma rays originating from Earth, called terrestrial gamma ray flashes (TGFsMeasurements and implications of the relationship between lightning and terrestrial gamma ray associated with 26 terrestrial gamma ray flashes (TGFs) recorded by the RHESSI satellite over the Caribbean

  3. Results from the Milagro Gamma-Ray Observatory E. Blaufuss a

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    V emission from the galactic plane, and a search for transient emission above 100 GeV from gamma ray bursts- clei (AGN), supernova remnants and gamma-ray bursts (GRB). Gamma rays are also produced when high1 Results from the Milagro Gamma-Ray Observatory E. Blaufuss a for the Milagro Collaboration

  4. Gamma Ray Bursts as seen by a Giant Air Shower Array

    E-Print Network [OSTI]

    C. O. Escobar; P. L. Da Silva; R. A. Vázquez

    1997-12-19T23:59:59.000Z

    The potentiality of a Giant Shower Array to low energy gamma rays from gamma ray bursts is discussed. Effective areas are calculated for different scenarios and the results are encouraging. If gamma ray bursts have a spectrum which continues in the high energy gamma ray region, the Pierre Auger Observatory will be able to detect it.

  5. Gamma-ray emission from binaries in context

    E-Print Network [OSTI]

    Dubus, Guillaume

    2015-01-01T23:59:59.000Z

    More than a dozen binary systems are now established as sources of variable, high energy (HE, 0.1-100 GeV) gamma rays. Five are also established sources of very high energy (VHE, >100 GeV) gamma rays. The mechanisms behind gamma-ray emission in binaries are very diverse. My current understanding is that they divide up into four types of systems: gamma-ray binaries, powered by pulsar rotation; microquasars, powered by accretion onto a black hole or neutron star; novae, powered by thermonuclear runaway on a white dwarf; colliding wind binaries, powered by stellar winds from massive stars. Some of these types had long been suspected to emit gamma rays (microquasars), others have taken the community by surprise (novae). My purpose here is to provide a brief review of the current status of gamma-ray emission from binaries, in the context of related objects where similar mechanisms are at work (pulsar wind nebulae, active galactic nuclei, supernova remnants).

  6. Delayed Gamma-Ray Spectroscopy for Spent Nuclear Fuel Assay

    SciTech Connect (OSTI)

    Campbell, Luke W.; Hunt, Alan W.; Ludewigt, Bernhard A.; Mozin, Vladimir V.

    2012-04-01T23:59:59.000Z

    High-energy, beta-delayed gamma-ray spectroscopy is investigated as a non-destructive assay technique for the determination of plutonium mass in spent nuclear fuel. This approach exploits the unique isotope-specific signatures contained in the delayed gamma-ray emission spectra detected following active interrogation with an external neutron source. A high fidelity modeling approach is described that couples radiation transport, analytical decay/depletion, and a newly developed gamma-ray emission source reconstruction code. Initially simulated and analyzed was a “one-pass” delayed gamma-ray assay that focused on the long-lived signatures. Also presented are the results of an independent study that investigated “pulsed mode” measurements, to capture the more isotope-specific, short-lived signatures. Initial modeling results outlined in this paper suggest that delayed gamma-ray assay of spent nuclear fuel assemblies can be accomplished with a neutron generator of sufficient strength and currently available gamma-ray detectors.

  7. Milagro - A TeV Observatory for Gamma Ray Bursts

    SciTech Connect (OSTI)

    Dingus, B.L. [Los Alamos National Laboratory (United States)

    2004-09-28T23:59:59.000Z

    Milagro is a large field of view ({approx} 2 sr), high duty cycle ({approx}90%), ground-based observatory sensitive to gamma-rays above {approx}100 GeV. This unique detector is ideal for observing the highest energy gamma-rays from gamma-ray bursts. The highest energy gamma rays supply very strong constraints on the nature of gamma-ray burst sources as well as fundamental physics. Because the highest energy gamma-rays are attenuated by pair production with the extragalactic infrared background light, Milagro's sensitivity decreases rapidly for bursts with redshift > 0.5. While only 10 % of bursts have been measured to be within z=0.5, these bursts are very well studied at all wavelengths resulting in the most complete understanding of GRB phenomena. Milagro has sufficient sensitivity in units of E2 dN/dE to detect VHE luminosities lower than the observed luminosities at {approx} 100 keV for these nearby bursts. Therefore, the launch of SWIFT and its ability to localize and measure redshifts of many bursts points to great future possibilities.

  8. Experimental investigation of silicon photomultipliers as compact light readout systems for gamma-ray spectroscopy applications in fusion plasmas

    SciTech Connect (OSTI)

    Nocente, M., E-mail: massimo.nocente@mib.infn.it; Gorini, G. [Dipartimento di Fisica “G. Occhialini,” Universitŕ degli Studi di Milano-Bicocca, Milano (Italy); Istituto di Fisica del Plasma “P. Caldirola,” EURATOM-ENEA-CNR Association, Milano (Italy); Fazzi, A.; Lorenzoli, M.; Pirovano, C. [Dipartimento di Energia, CeSNEF, Politecnico di Milano, Milano (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Milano (Italy); Tardocchi, M. [Istituto di Fisica del Plasma “P. Caldirola,” EURATOM-ENEA-CNR Association, Milano (Italy); Cazzaniga, C.; Rebai, M. [Dipartimento di Fisica “G. Occhialini,” Universitŕ degli Studi di Milano-Bicocca, Milano (Italy); Uboldi, C.; Varoli, V. [Dipartimento di Energia, CeSNEF, Politecnico di Milano, Milano (Italy)

    2014-11-15T23:59:59.000Z

    A matrix of Silicon Photo Multipliers has been developed for light readout from a large area 1 in. × 1 in. LaBr{sub 3} crystal. The system has been characterized in the laboratory and its performance compared to that of a conventional photo multiplier tube. A pulse duration of 100 ns was achieved, which opens up to spectroscopy applications at high counting rates. The energy resolution measured using radioactive sources extrapolates to 3%–4% in the energy range E{sub ?} = 3–5 MeV, enabling gamma-ray spectroscopy measurements at good energy resolution. The results reported here are of relevance in view of the development of compact gamma-ray detectors with spectroscopy capabilities, such as an enhanced gamma-ray camera for high power fusion plasmas, where the use of photomultiplier is impeded by space limitation and sensitivity to magnetic fields.

  9. HETEROGENEITY IN SHORT GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Norris, Jay P. [Physics and Astronomy Department, University of Denver, Denver, CO 80208 (United States); Gehrels, Neil [Astroparticle Physics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Scargle, Jeffrey D. [Space Science and Astrobiology Division, NASA/Ames Research Center, Moffett Field, CA 94035-1000 (United States)

    2011-07-01T23:59:59.000Z

    We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample is comprised of 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales-durations, pulse structure widths, and peak intervals-for EE bursts are factors of {approx}2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts-the anti-correlation of pulse intensity and width-continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition, we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/X-Ray Telescope (XRT). The median flux of the initial XRT detections for EE bursts ({approx}6x10{sup -10} erg cm{sup -2} s{sup -1}) is {approx}>20x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts ({approx}60,000 s) is {approx}30x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into denser environments than non-EE bursts, or that the sometimes-dominant EE component efficiently powers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

  10. Time-of-flight discrimination between gamma-rays and neutrons by using artificial neural networks

    E-Print Network [OSTI]

    Akkoyun, Serkan

    2012-01-01T23:59:59.000Z

    The gamma-ray tracking detector arrays, such as advanced gamma ray tracking array (AGATA), are quite powerful detection systems in nuclear structure physic studies. In these arrays, the sequences of the gamma-ray interaction points in the detectors can correctly be identified in order to obtain true gamma-ray energies emitted from the nuclei of interest. Together with the gamma-rays, a number of neutrons are also emitted from the nuclei and these neutrons influence gamma-ray spectra. An obvious method of separating between neutrons and gamma-rays is based on the time-of-flight (tof) technique. This work aims obtaining tof distributions of gamma-rays and neutrons by using feed-forward artificial neural network (ANN). It was shown that, ANN can correctly classify gamma-ray and neutron events. Testing of trained networks on experimental data clearly shows up tof discrimination of gamma-rays and neutrons.

  11. DISCOVERY OF TeV GAMMA-RAY EMISSION FROM CTA 1 BY VERITAS

    SciTech Connect (OSTI)

    Aliu, E.; Errando, M. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States)] [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Archambault, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada)] [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Arlen, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)] [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Aune, T.; Bouvier, A. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States)] [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R. [Department of Physics, Washington University, St. Louis, MO 63130 (United States)] [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)] [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Cesarini, A.; Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland)] [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States)] [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)] [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Cui, W. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)] [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Duke, C. [Department of Physics, Grinnell College, Grinnell, IA 50112-1690 (United States)] [Department of Physics, Grinnell College, Grinnell, IA 50112-1690 (United States); Dumm, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)] [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Dwarkadas, V. V. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States)] [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Falcone, A., E-mail: muk@astro.columbia.edu, E-mail: smcarthur@ulysses.uchicago.edu [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); and others

    2013-02-10T23:59:59.000Z

    We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semimajor (semiminor) axis 0. Degree-Sign 30 (0. Degree-Sign 24) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N {sub 0}(E/3 TeV){sup -{Gamma}}, with a differential spectral index of {Gamma} = 2.2 {+-} 0.2{sub stat} {+-} 0.3{sub sys}, and normalization N {sub 0} = (9.1 {+-} 1.3{sub stat} {+-} 1.7{sub sys}) Multiplication-Sign 10{sup -14} cm{sup -2} s{sup -1} TeV{sup -1}. The integral flux, F {sub {gamma}} = 4.0 Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} above 1 TeV, corresponds to 0.2% of the pulsar spin-down power at 1.4 kpc. The energetics, colocation with the SNR, and the relatively small extent of the TeV emission strongly argue for the PWN origin of the TeV photons. We consider the origin of the TeV emission in CTA 1.

  12. Space Sci Rev DOI 10.1007/s11214-012-9894-0

    E-Print Network [OSTI]

    Cummer, Steven A.

    and gamma-rays. These emissions appear over wide timescales, ranging from sub- microsecond bursts of x-rays associated with lightning leaders, to sub-millisecond bursts of gamma-rays seen in space called terrestrial and accompanying x-ray and gamma-ray emissions. Terrestrial gamma-ray flashes (TGFs), bright bursts of multi

  13. Are gamma-ray bursts the sources of ultra-high energy cosmic rays?

    E-Print Network [OSTI]

    Philipp Baerwald; Mauricio Bustamante; Walter Winter

    2014-07-07T23:59:59.000Z

    We reconsider the possibility that gamma-ray bursts (GRBs) are the sources of the ultra-high energy cosmic rays (UHECRs) within the internal shock model, assuming a pure proton composition of the UHECRs. For the first time, we combine the information from gamma-rays, cosmic rays, prompt neutrinos, and cosmogenic neutrinos quantitatively in a joint cosmic ray production and propagation model, and we show that the information on the cosmic energy budget can be obtained as a consequence. In addition to the neutron model, we consider alternative scenarios for the cosmic ray escape from the GRBs, i.e., that cosmic rays can leak from the sources. We find that the dip model, which describes the ankle in UHECR observations by the pair production dip, is strongly disfavored in combination with the internal shock model because a) unrealistically high baryonic loadings (energy in protons versus energy in electrons/gamma-rays) are needed for the individual GRBs and b) the prompt neutrino flux easily overshoots the corresponding neutrino bound. On the other hand, GRBs may account for the UHECRs in the ankle transition model if cosmic rays leak out from the source at the highest energies. In that case, we demonstrate that future neutrino observations can efficiently test most of the parameter space -- unless the baryonic loading is much larger than previously anticipated.

  14. Coincidence searches of gravitational waves and short gamma-ray bursts

    E-Print Network [OSTI]

    Andrea Maselli; Valeria Ferrari

    2014-05-28T23:59:59.000Z

    Black-hole neutron-star coalescing binaries have been invoked as one of the most suitable scenario to explain the emission of short gamma-ray bursts. Indeed, if the black-hole which forms after the merger, is surrounded by a massive disk, neutrino annihilation processes may produce high-energy and collimated electromagnetic radiation. In this paper, we devise a new procedure, to be used in the search for gravitational waves from black-hole-neutron-star binaries, to assign a probability that a detected gravitational signal is associated to the formation of an accreting disk, massive enough to power gamma-ray bursts. This method is based on two recently proposed semi-analytic fits, one reproducing the mass of the remnant disk surrounding the black hole as a function of some binary parameters, the second relating the neutron star compactness, with its tidal deformability. Our approach can be used in low-latency data analysis to restrict the parameter space searching for gravitational signals associated with short gamma-ray bursts, and to gain information on the dynamics of the coalescing system and on the neutron star equation of state.

  15. Radio to gamma-ray variability study of blazar S5 0716+714

    E-Print Network [OSTI]

    Rani, B; Fuhrmann, L; Boettcher, M; Lott, B; Aller, H D; Aller, M F; Angelakis, E; Bach, U; Bastieri, D; Falcone, A D; Fukazawa, Y; Gabanyi, K E; Gupta, A C; Gurwell, M; Itoh, R; Kawabata, K S; Krips, M; Lähteenmäki, A A; Liu, X; Marchili, N; Max-Moerbeck, W; Nestoras, I; Nieppola, E; Quintana-Lacaci, G; Readhead, A C S; Richards, J L; Sasada, M; Sievers, A; Sokolovsky, K; Stroh, M; Tammi, J; Tornikoski, M; Uemura, M; Ungerechts, H; Urano, T; Zensus, J A

    2013-01-01T23:59:59.000Z

    We present the results of a series of radio, optical, X-ray and gamma-ray observations of the BL Lac object S50716+714 carried out between April 2007 and January 2011. The multi-frequency observations were obtained using several ground and space based facilities. The intense optical monitoring of the source reveals faster repetitive variations superimposed on a long-term variability trend at a time scale of ~350 days. Episodes of fast variability recur on time scales of ~ 60-70 days. The intense and simultaneous activity at optical and gamma-ray frequencies favors the SSC mechanism for the production of the high-energy emission. Two major low-peaking radio flares were observed during this high optical/gamma-ray activity period. The radio flares are characterized by a rising and a decaying stage and are in agreement with the formation of a shock and its evolution. We found that the evolution of the radio flares requires a geometrical variation in addition to intrinsic variations of the source. Different estima...

  16. Gamma-Ray Bursts from Radio-Quiet Quasars

    E-Print Network [OSTI]

    N. Schartel; H. Andernach; J. Greiner

    1996-12-16T23:59:59.000Z

    We study positional coincidences between gamma-ray bursts in the BATSE 3B catalogue and quasars/AGN taken from the Veron-Cetty & Veron compilation. For most classes of AGN, for BL Lac objects and for radio-loud quasars, we find no excess coincidences above random expectation, and we give upper limits for their burst emission rate. However, surprising evidence is found for a positional correlation between gamma-ray bursts and radio-quiet quasars. A total of 134 selected bursts with a position error radius 99.7% to be associated with each other. An analysis of a smaller sample of well-localized interplanetary network gamma-ray burst positions supports this result. This correlation strongly favours the cosmological origin of gamma-ray bursts and enables to estimate its distance scale. The average luminosity of those gamma-ray bursts which we associate directly with radio-quiet quasars is of the order of 4*10^52 erg (assuming isotropic emission).

  17. AN OBSERVATIONAL IMPRINT OF THE COLLAPSAR MODEL OF LONG GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Bromberg, Omer; Piran, Tsvi; Sari, Re'em [Racah Institute of Physics, Hebrew University, 91904 Jerusalem (Israel); Nakar, Ehud [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv (Israel)

    2012-04-20T23:59:59.000Z

    The Collapsar model provides a theoretical framework for the well-known association between long gamma-ray bursts (GRBs) and collapsing massive stars. A bipolar relativistic jet, launched at the core of a collapsing star, drills its way through the stellar envelope and breaks out of the surface before producing the observed gamma rays. While a wealth of observations associate GRBs with the death of massive stars, as yet there is no direct evidence for the Collapsar model itself. Here we show that a distinct signature of the Collapsar model is the appearance of a plateau in the duration distribution of the prompt GRB emission at times much shorter than the typical breakout time of the jet. This plateau is evident in the data of all three major satellites. Our findings provide evidence that directly supports the Collapsar model. In addition, the model suggests the existence of a large population of choked (failed) GRBs, and implies that the 2 s duration commonly used to separate Collapsars and non-Collapsars is inconsistent with the duration distributions of Swift and Fermi GRBs and only holds for BATSE GRBs.

  18. DISCOVERY OF A NEW TeV GAMMA-RAY SOURCE: VER J0521+211

    SciTech Connect (OSTI)

    Archambault, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Arlen, T.; Aune, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Behera, B.; Federici, S. [DESY, Platanenallee 6, D-15738 Zeuthen (Germany); Beilicke, M.; Buckley, J. H.; Bugaev, V. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Bird, R. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Bouvier, A. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Byrum, K. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Cesarini, A.; Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Cui, W.; Feng, Q.; Finley, J. P. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Errando, M. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Falcone, A., E-mail: fortin@veritas.sao.arizona.edu, E-mail: errando@astro.columbia.edu, E-mail: jholder@physics.udel.edu, E-mail: sfegan@llr.in2p3.fr [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Collaboration: VERITAS Collaboration; and others

    2013-10-20T23:59:59.000Z

    We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov Telescope Array. These observations were motivated by the discovery of a cluster of >30 GeV photons in the first year of Fermi Large Area Telescope observations. VER J0521+211 is relatively bright at TeV energies, with a mean photon flux of (1.93 ± 0.13{sub stat} ± 0.78{sub sys}) × 10{sup –11} cm{sup –2} s{sup –1} above 0.2 TeV during the period of the VERITAS observations. The source is strongly variable on a daily timescale across all wavebands, from optical to TeV, with a peak flux corresponding to ?0.3 times the steady Crab Nebula flux at TeV energies. Follow-up observations in the optical and X-ray bands classify the newly discovered TeV source as a BL Lac-type blazar with uncertain redshift, although recent measurements suggest z = 0.108. VER J0521+211 exhibits all the defining properties of blazars in radio, optical, X-ray, and gamma-ray wavelengths.

  19. Constraints on Blazar Jet Conditions During Gamma-Ray Flaring from Radiative Transfer Modeling

    E-Print Network [OSTI]

    Aller, Margo F; Aller, Hugh D; Hovatta, Talvikki

    2013-01-01T23:59:59.000Z

    As part of a program to investigate jet flow conditions during GeV gamma-ray flares detected by Fermi, we are using UMRAO multi-frequency, centimeter-band total flux density and linear polarization monitoring observations to constrain radiative transfer models incorporating propagating shocks orientated at an arbitrary angle to the flow direction. We describe the characteristics of the model, illustrate how the data are used to constrain the models, and present results for three program sources with diverse characteristics: PKS 0420-01, OJ 287, and 1156+295. The modeling of the observed spectral behavior yields information on the sense, strength and orientation of the shocks producing the radio-band flaring; on the energy distribution of the radiating particles; and on the observer's viewing angle with respect to the jet independent of VLBI data. We present evidence that, while a random component dominates the jet magnetic field, a distinguishing feature of those radio events with an associated gamma-ray flar...

  20. GRB 091024A and the nature of ultra-long gamma-ray bursts

    SciTech Connect (OSTI)

    Virgili, F. J.; Mundell, C. G.; Harrison, R.; Kobayashi, S.; Steele, I. A.; Mottram, C. J.; Clay, N. R. [Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF (United Kingdom); Pal'shin, V. [Ioffe Physical Technical Institute, St. Petersburg 194021 (Russian Federation); Guidorzi, C. [Department of Physics and Earth Sciences, University of Ferrara, Via Saragat, 1, I-44122 Ferrara (Italy); Margutti, R.; Chornock, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Melandri, A. [INAF/Brera Astronomical Observatory, via Bianchi 46, I-23807 Merate (Italy); Henden, A. [AAVSO, 49 Bay State Road, Cambridge, MA 02138 (United States); Updike, A. C. [Department of Chemistry and Physics, Roger Williams University, Bristol, RI 02809 (United States); Cenko, S. B. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Tanvir, N. R. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Cucchiara, A. [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Gomboc, A. [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Levan, A. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Cano, Z., E-mail: F.J.Virgili@ljmu.ac.uk [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, 107 Reykjavik (Iceland); and others

    2013-11-20T23:59:59.000Z

    We present a broadband study of gamma-ray burst (GRB) 091024A within the context of other ultra-long-duration GRBs. An unusually long burst detected by Konus-Wind (KW), Swift, and Fermi, GRB 091024A has prompt emission episodes covering ?1300 s, accompanied by bright and highly structured optical emission captured by various rapid-response facilities, including the 2 m autonomous robotic Faulkes North and Liverpool Telescopes, KAIT, S-LOTIS, and the Sonoita Research Observatory. We also observed the burst with 8 and 10 m class telescopes and determine the redshift to be z = 1.0924 ± 0.0004. We find no correlation between the optical and ?-ray peaks and interpret the optical light curve as being of external origin, caused by the reverse and forward shock of a highly magnetized jet (R{sub B} ? 100-200). Low-level emission is detected throughout the near-background quiescent period between the first two emission episodes of the KW data, suggesting continued central-engine activity; we discuss the implications of this ongoing emission and its impact on the afterglow evolution and predictions. We summarize the varied sample of historical GRBs with exceptionally long durations in gamma-rays (?1000 s) and discuss the likelihood of these events being from a separate population; we suggest ultra-long GRBs represent the tail of the duration distribution of the long GRB population.

  1. Insights into the particle acceleration of a peculiar gamma -ray radio galaxy IC 310

    E-Print Network [OSTI]

    Sitarek, J; Mannheim, K; Colin, P; Kadler, M; Schultz, R; Krauß, F; Ros, E; Bach, U; Wilms, J

    2015-01-01T23:59:59.000Z

    IC 310 has recently been identified as a gamma-ray emitter based on observations at GeV energies with Fermi-LAT and at very high energies (VHE, E > 100 GeV) with the MAGIC telescopes. Despite IC 310 having been classified as a radio galaxy with the jet observed at an angle > 10 degrees, it exhibits a mixture of multiwavelength properties of a radio galaxy and a blazar, possibly making it a transitional object. On the night of 12/13th of November 2012 the MAGIC telescopes observed a series of violent outbursts from the direction of IC 310 with flux-doubling time scales faster than 5 min and a peculiar spectrum spreading over 2 orders of magnitude. Such fast variability constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole, challenging the shock acceleration models, commonly used in explanation of gamma-ray radiation from active galaxies. Here we will show that this emission can be associated with pulsar-like particle acceleration by the electric...

  2. Gamma Ray Bursts as Possible High Energy Sources

    E-Print Network [OSTI]

    Charles D. Dermer

    2005-12-06T23:59:59.000Z

    Gamma-ray bursts are known to be sources of high-energy gamma rays, and are likely to be sources of high-energy cosmic rays and neutrinos. Following a short review of observations of GRBs at multi-MeV energies and above, the physics of leptonic and hadronic models of GRBs is summarized. Evidence for two components in BATSE and EGRET/TASC data suggest that GRBs are sources of high-energy cosmic rays. GLAST observations will reveal the high-energy gamma-ray power and energy releases from GRBs, and will provide detailed knowledge of anomalous high-energy emission components, but confirmation of cosmic ray acceleration must await 100 TeV -- PeV neutrino detection from GRBs.

  3. High energy gamma rays from old accreting neutron stars

    E-Print Network [OSTI]

    P. Blasi

    1996-06-28T23:59:59.000Z

    We consider a magnetized neutron star with accretion from a companion star or a gas cloud around it, as a possible source of gamma rays with energy between $100$ $MeV$ and $10^{14}-10^{16}~eV$. The flow of the accreting plasma is terminated by a shock at the Alfv\\'en surface. Such a shock is the site for the acceleration of particles up to energies of $\\sim 10^{15}-10^{17}~eV$; gamma photons are produced in the inelastic $pp$ collisions between shock-accelerated particles and accreting matter. The model is applied to old neutron stars both isolated or in binary systems. The gamma ray flux above $100~MeV$ is not easily detectable, but we propose that gamma rays with very high energy could be used by Cherenkov experiments as a possible signature of isolated old neutron stars in dense clouds in our galaxy.

  4. Gamma-Ray Bursts and Topology of the Universe

    E-Print Network [OSTI]

    Marek Biesiada

    1993-10-04T23:59:59.000Z

    In this letter we propose a physical explanation for recently reported correlations between pairs of close and antipodal gamma-ray bursts from publicly available BATSE catalogue. Our model is based on the cosmological scenario in which bursters are located at cosmological distances of order of 0.5--2~Gpc. Observed distribution of gamma-ray bursts strongly suports this assumption. If so gamma-ray bursts may provide a very good probe for investigating the topological structure of the Universe. We notice that correlation between antipodal events may in fact indicate that we live in the so called Ellis' small universe which has Friedman-Roberston-Walker metric structure and nontrivial topology.

  5. Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification

    SciTech Connect (OSTI)

    John Kavouras; Xianfei Wen; Daren R. Norman; Dante R. Nakazawa; Haori Yang

    2012-11-01T23:59:59.000Z

    Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. High-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. After photofission reactions, delayed signals are easily distinguishable from the interrogating radiation. Linac-based, advanced inspection techniques utilizing the fission signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope. Isotopic composition measurement methods based on delayed gamma ray spectroscopy will be the primary focus of this work.

  6. Pulser injection with subsequent removal for gamma-ray spectrometry

    DOE Patents [OSTI]

    Hartwell, Jack K. (Idaho Falls, ID); Goodwin, Scott G. (Idaho Falls, ID); Johnson, Larry O. (Blackfoot, ID); Killian, E. Wayne (Idahoe Falls, ID)

    1990-01-01T23:59:59.000Z

    An improved system for gamma-ray spectroscopy characterized by an interface module that controls the injection of electronic pulses as well as separation logic that enables storage of pulser events in a region of the spectrum of a multichannel analyzer distinct from the region reserved for storage of gamma-ray events. The module accomplishes this by tagging pulser events (high or low) injected into the amplification circuitry, adding an offset to the events so identified at the time the events are at the output of the analog to digital converter, and storing such events in the upper portion of the spectrum stored in the multichannel analyzer. The module can be adapted for use with existing gamma-ray spectroscopy equipment to provide for automatic analyses of radioisotopes.

  7. Linking Short Gamma Ray Bursts and their Host Galaxies

    E-Print Network [OSTI]

    James E. Rhoads

    2008-07-16T23:59:59.000Z

    The luminosities of short gamma ray burst host galaxies are anticorrelated with both the isotropic equivalent gamma ray energy and the gamma ray luminosity of the explosions. Observational selection effects only strengthen the significance of this correlation. The correlation may indicate that there are two physically distinct groups of SGRBs. If so, it requires that the more luminous class of explosions be associated with the younger class of progenitors. Alternatively, it could be due to a continuous distribution of burst and host properties. As one possible explanation, we find that the effect of binary neutron star masses on inspiral time and energy reservoir produces a correlation of the appropriate sign, but does not automatically reproduce the correlation slope or the full range of SGRB energy scales. Any future model of SGRB progenitors needs to reproduce this correlation.

  8. A Gamma-Ray Burst/Pulsar for Cosmic-Ray Positrons with a Dark Matter-like Spectrum

    E-Print Network [OSTI]

    Kunihito Ioka

    2010-06-15T23:59:59.000Z

    We propose that a nearby gamma-ray burst (GRB) or GRB-like (old, single and short-lived) pulsar/supernova remnant/microquasar about 10^{5-6} years ago may be responsible for the excesses of cosmic-ray positrons and electrons recently observed by the PAMELA, ATIC/PPB-BETS, Fermi and HESS experiments. We can reproduce the smooth Fermi/HESS spectra as well as the spiky ATIC/PPB-BETS spectra. The spectra have a sharp cutoff that is similar to the dark matter predictions, sometimes together with a line (not similar), since higher energy cosmic-rays cool faster where the cutoff/line energy marks the source age. A GRB-like astrophysical source is expected to have a small but finite spread in the cutoff/line as well as anisotropy in the cosmic-ray and diffuse gamma-ray flux, providing a method for the Fermi and future CALET experiments to discriminate between dark matter and astrophysical origins.

  9. Outcrop gamma-ray logging applied to subsurface petroleum geology

    SciTech Connect (OSTI)

    Slatt, R.M.; Borer, J.M.; Horn, B.W. [Colorado School of Mines, Golden, CO (United States)] [and others

    1995-10-01T23:59:59.000Z

    Developing a gamma-ray log profile of an outcrop with a hand-held scintillometer has many applications to subsurface petroleum geology. The outcrop gamma-ray log provides a readily understandable bridge between what is observed in outcrop and what is to be interpreted on well logs and seismic records. Several examples are presented in this paper that demonstrate major applications. An outcrop from the Cretaceous Mesaverde Group in Colorado provides an excellent example of the use of outcrop gamma-ray logs to better visualize spatial variability of depositional settings for improved well log correlations. Out crops from the Cretaceous Almond Formation, Niobrara Formation, and Graneros Shale in Colorado serve as examples of outcrop gamma-ray logging used to correlate outcrops with their subsurface equivalents for improved lithologic and stratigraphic interpretation of well logs. Outcrops of the Cretaceous Sharon Springs Member of the Pierre Shale in Colorado and the Eocene Green River Formation in Wyoming provide examples of the application of outcrop-gamma ray logging to identify and characterize organic-rich shales in outcrops and on well logs. Outcrops of the Pennsylvanian Jackfork Formation in Arkansas demonstrate the use of outcrop logging to yield improved interpretation of reservoir quality on well logs and for one- and two-dimensional seismic modeling. An outcrop of Precambrian and Cambro-Ordovician rocks from Algeria provides an example of outcrop logging to recognize unconformities and other major surfaces on well logs. An outcrop of the Niobrara Formation in Colorado is used as an example for improved understanding of horizontal gamma-ray log response. The example logs presented are all drived with a hand-held scintillometer. This technique is simple, quick, and relatively inexpensive, so is recommended for any outcrop work that is intended to be applied t;o subsurface well logs or seismic interpretation.

  10. Gamma Ray Bursts: recent results and connections to very high energy Cosmic Rays and Neutrinos

    E-Print Network [OSTI]

    Péter Mészáros; Katsuaki Asano; Péter Veres

    2012-09-11T23:59:59.000Z

    Gamma-ray bursts are the most concentrated explosions in the Universe. They have been detected electromagnetically at energies up to tens of GeV, and it is suspected that they could be active at least up to TeV energies. It is also speculated that they could emit cosmic rays and neutrinos at energies reaching up to the $10^{18}-10^{20}$ eV range. Here we review the recent developments in the photon phenomenology in the light of \\swift and \\fermi satellite observations, as well as recent IceCube upper limits on their neutrino luminosity. We discuss some of the theoretical models developed to explain these observations and their possible contribution to a very high energy cosmic ray and neutrino background.

  11. The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts

    E-Print Network [OSTI]

    Zhang, Bing

    2010-01-01T23:59:59.000Z

    The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests a Poynting-flux-dominated outflow. We propose a model of gamma-ray burst (GRB) prompt emission in the Poynting-flux-dominated regime, namely, the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. It is envisaged that the GRB central engine launches an intermittent, magnetically-dominated wind, and that in the GRB emission region, the ejecta is still moderately magnetized. Similar to the internal shock (IS) model, the mini-shells interact internally at the traditional internal shock radius. Most of these early collision have little energy dissipation, but serve to distort the ordered magnetic field lines. At a certain point, the distortion of magnetic field configuration reaches the critical condition to allow fast reconnection seeds to occur, which induce relativistic MHD turbulence in the interaction regions. The turbulence further...

  12. Modeling Bright Gamma-ray and Radio Emission at Fast Cloud Shocks

    E-Print Network [OSTI]

    Lee, Shiu-Hang; Raymond, John C; Nagataki, Shigehiro; Slane, Patrick O; Ellison, Donald C

    2015-01-01T23:59:59.000Z

    Recent observations by the Large Area Telescope (LAT) onboard the Fermi satellite have revealed bright gamma-ray emission from middle-aged supernova remnants (SNRs) inside our Galaxy. These remnants, which also possess bright non-thermal radio shells, are often found to be interacting directly with surrounding gas clouds. We explore the non-thermal emission mechanism at these dynamically evolved SNRs by constructing a hydrodynamical model. Two scenarios of particle acceleration, either a re-acceleration of Galactic cosmic rays (CRs) or an efficient nonlinear diffusive shock acceleration (NLDSA) of particles injected from downstream, are considered. Using parameters inferred from observations, our models are contrasted with the observed spectra of SNR W44. For the re-acceleration case, we predict a significant enhancement of radio and GeV emission as the SNR undergoes a transition into the radiative phase. If sufficiently strong magnetic turbulence is present in the molecular cloud, the re-acceleration scenari...

  13. Confronting the Galactic Center Gamma Ray Excess With a Light Scalar Dark Matter

    E-Print Network [OSTI]

    Dilip Kumar Ghosh; Subhadeep Mondal; Ipsita Saha

    2015-01-26T23:59:59.000Z

    The Fermi Large Area Telescope observed an excess in gamma ray emission spectrum coming from the center of the Milky Way galaxy. This data reveals that a light Dark Matter (DM) candidate of mass in the range 31-40 GeV, dominantly decaying into $b\\bar b$ final state, can explain the presence of the observed bump in photon energy. We try to interpret this observed phenomena by sneutrino DM annihilation into pair of fermions in the Supersymmetric Inverse Seesaw Model (SISM). This model can also account for tiny non-zero neutrino masses satisfying existing neutrino oscillation data. We show that a Higgs portal DM in this model is in perfect agreement with this new interpretation besides satisfying all other existing collider, cosmological and low energy experimental constraints.

  14. Improved Limits on Sterile Neutrino Dark Matter using Full-Sky Fermi-GBM Data

    E-Print Network [OSTI]

    Ng, Kenny C Y; Gaskins, Jennifer M; Smith, Miles; Preece, Robert

    2015-01-01T23:59:59.000Z

    A sterile neutrino of ~keV mass is a well motivated dark matter candidate. Its decay generates a X-ray line which offers a unique target for X-ray telescopes. For the first time, we use the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope to search for sterile neutrino decay lines; our analysis covers the energy range 10-25 keV (sterile neutrino mass 20-50 keV), which is inaccessible to X-ray and gamma-ray satellites such as Chandra, Suzaku, XMM-Newton, and INTEGRAL. The extremely wide field of view of the GBM enables a large fraction of the Milky Way dark matter halo to be probed. After implementing careful data cuts, we obtain ~53 days of full sky observational data. We search for sterile neutrino decay lines in the energy spectrum, and find no significant signal. From this, we obtain upper limits on the sterile neutrino mixing angle as a function of mass. In the sterile neutrino mass range 25-40 keV, we improve upon previous upper limits by approximately an order of magnitude. Bett...

  15. In-Flight Measurement of the Absolute Energy Scale of the Fermi Large Area Telescope

    SciTech Connect (OSTI)

    Ackermann, M.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Ajello, M.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Allafort, A.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm; Baldini, L.; /INFN, Pisa; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Bloom, E.D.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Bouvier, A.; /UC, Santa Cruz; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari Polytechnic /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /Stanford U., HEPL /SLAC /KIPAC, Menlo Park; Buson, S.; /INFN, Padua /Padua U. /CSIC, Catalunya /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Unlisted, US /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /ASDC, Frascati /Perugia U. /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Montpellier U. /ASDC, Frascati /Bari Polytechnic /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Montpellier U. /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Ecole Polytechnique /Hiroshima U. /Stanford U., HEPL /SLAC /KIPAC, Menlo Park /Bari Polytechnic /INFN, Bari /INFN, Bari /NASA, Goddard /INFN, Perugia /Perugia U.; /more authors..

    2012-09-20T23:59:59.000Z

    The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron-plus-positron (CRE) spectrum in low Earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between {approx}6 and {approx}13 GeV with an estimated uncertainty of {approx}2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.

  16. A Gamma-Ray Bursts' Fluence-Duration Correlation

    E-Print Network [OSTI]

    Istvan Horvath; Lajos G. Balazs; Peter Meszaros; Zsolt Bagoly; Attila Meszaros

    2005-08-01T23:59:59.000Z

    We present an analysis indicating that there is a correlation between the fluences and the durations of gamma-ray bursts, and provide arguments that this reflects a correlation between the total emitted energies and the intrinsic durations. For the short (long) bursts the total emitted energies are roughly proportional to the first (second) power of the intrinsic duration. This difference in the energy-duration relationship is statistically significant, and may provide an interesting constraint on models aiming to explain the short and long gamma-ray bursts.

  17. Correlation between Gamma-Ray bursts and Gravitational Waves

    E-Print Network [OSTI]

    P. Tricarico; A. Ortolan; A. Solaroli; G. Vedovato; L. Baggio; M. Cerdonio; L. Taffarello; J. Zendri; R. Mezzena; G. A. Prodi; S. Vitale; P. Fortini; M. Bonaldi; P. Falferi

    2001-01-05T23:59:59.000Z

    The cosmological origin of $\\gamma$-ray bursts (GRBs) is now commonly accepted and, according to several models for the central engine, GRB sources should also emit at the same time gravitational waves bursts (GWBs). We have performed two correlation searches between the data of the resonant gravitational wave detector AURIGA and GRB arrival times collected in the BATSE 4B catalog. No correlation was found and an upper limit \\bbox{$h_{\\text{RMS}} \\leq 1.5 \\times 10^{-18}$} on the averaged amplitude of gravitational waves associated with $\\gamma$-ray bursts has been set for the first time.

  18. Gamma-ray Burst Models: General Requirements and Predictions

    E-Print Network [OSTI]

    P. Meszaros

    1995-02-21T23:59:59.000Z

    Whatever the ultimate energy source of gamma-ray bursts turns out to be, the resulting sequence of physical events is likely to lead to a fairly generic, almost unavoidable scenario: a relativistic fireball that dissipates its energy after it has become optically thin. This is expected both for cosmological and halo distances. Here we explore the observational motivation of this scenario, and the consequences of the resulting models for the photon production in different wavebands, the energetics and the time structure of classical gamma-ray bursters.

  19. X-ray afterglows from gamma-ray bursts

    E-Print Network [OSTI]

    M. Tavani

    1997-03-24T23:59:59.000Z

    We consider possible interpretations of the recently detected X- ray afterglow from the gamma-ray burst source GRB 970228. Cosmological and Galactic models of gamma-ray bursts predict different flux and spectral evolution of X-ray afterglows. We show that models based on adiabatic expansion of relativistic forward shocks require very efficient particle energization or post-burst re-acceleration during the expansion. Cooling neutron star models predict a very distinctive spectral and flux evolution that can be tested in current X-ray data.

  20. GAMQUEST, A computer program to identify gamma rays

    SciTech Connect (OSTI)

    Brown, E.

    1994-05-01T23:59:59.000Z

    This paper describes the application of the computer program GAMQUEST to the study of gamma-ray spectra. The program is especially suited to the analysis of samples produced by neutron activation, and of environmental samples containing radioactive pollutants. GAMQUEST searches a large database (with data for over 60,000 gamma rays) to identify the various spectral lines from samples. The program runs on the VAX/6610 computer cluster of the Lawrence Berkeley Laboratory, and can be accessed from individual accounts or through Hepnet, Internet, or World Wide Web networks.

  1. Large-Scale Anisotropy of EGRET Gamma Ray Sources

    E-Print Network [OSTI]

    Luis Anchordoqui; Thomas McCauley; Thomas Paul; Olaf Reimer; Diego F. Torres

    2005-06-24T23:59:59.000Z

    In the course of its operation, the EGRET experiment detected high-energy gamma ray sources at energies above 100 MeV over the whole sky. In this communication, we search for large-scale anisotropy patterns among the catalogued EGRET sources using an expansion in spherical harmonics, accounting for EGRET's highly non-uniform exposure. We find significant excess in the quadrupole and octopole moments. This is consistent with the hypothesis that, in addition to the galactic plane, a second mid-latitude (5^{\\circ} < |b| < 30^{\\circ}) population, perhaps associated with the Gould belt, contributes to the gamma ray flux above 100 MeV.

  2. SWEPP Gamma-Ray Spectrometer System software design description

    SciTech Connect (OSTI)

    Femec, D.A.; Killian, E.W.

    1994-08-01T23:59:59.000Z

    To assist in the characterization of the radiological contents of contract-handled waste containers at the Stored Waste Examination Pilot Plant (SWEPP), the SWEPP Gamma-Ray Spectrometer (SGRS) System has been developed by the Radiation Measurements and Development Unit of the Idaho National Engineering Laboratory. The SGRS system software controls turntable and detector system activities. In addition to determining the concentrations of gamma-ray-emitting radionuclides, this software also calculates attenuation-corrected isotopic mass ratios of-specific interest. This document describes the software design for the data acquisition and analysis software associated with the SGRS system.

  3. First detection of >100 MeV gamma rays associated with a behind-the-limb solar flare

    E-Print Network [OSTI]

    Pesce-Rollins, Melissa; Petrosian, Vahe'; Liu, Wei; da Costa, Fatima Rubio; Allafort, Alice; Chen, Qingrong

    2015-01-01T23:59:59.000Z

    We report the first detection of >100 MeV gamma rays associated with a behind-the-limb solar flare, which presents a unique opportunity to probe the underlying physics of high-energy flare emission and particle acceleration. On 2013 October 11 a GOES M1.5 class solar flare occurred ~ 9.9 degrees behind the solar limb as observed by STEREO-B. RHESSI observed hard X-ray emission above the limb, most likely from the flare loop-top, as the footpoints were occulted. Surprisingly, the Fermi Large Area Telescope (LAT) detected >100 MeV gamma-rays for ~30 minutes with energies up to GeV. The LAT emission centroid is consistent with the RHESSI hard X-ray source, but its uncertainty does not constrain the source to be located there. The gamma-ray spectra can be adequately described by bremsstrahlung radiation from relativistic electrons having a relatively hard power-law spectrum with a high-energy exponential cutoff, or by the decay of pions produced by accelerated protons and ions with an isotropic pitch-angle distri...

  4. NO CORRELATION BETWEEN HOST GALAXY METALLICITY AND GAMMA-RAY ENERGY RELEASE FOR LONG-DURATION GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Levesque, Emily M.; Kewley, Lisa J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Soderberg, Alicia M.; Berger, Edo, E-mail: emsque@ifa.hawaii.ed, E-mail: kewley@ifa.hawaii.ed, E-mail: asoderbe@cfa.harvard.ed, E-mail: eberger@cfa.harvard.ed [Smithsonian Astrophysical Observatory, 60 Garden St., MS-20, Cambridge, MA 02138 (United States)

    2010-12-10T23:59:59.000Z

    We compare the redshifts, host galaxy metallicities, and isotropic (E{sub {gamma}},iso) and beaming-corrected (E{sub {gamma}}) gamma-ray energy release of 16 long-duration gamma-ray bursts (LGRBs) at z < 1. From this comparison, we find no statistically significant correlation between host metallicity and redshift, E{sub {gamma}},iso, or E{sub {gamma}}. These results are at odds with previous theoretical and observational predictions of an inverse correlation between gamma-ray energy release and host metallicity, as well as the standard predictions of metallicity-driven wind effects in stellar evolutionary models. We consider the implications that these results have for LGRB progenitor scenarios, and discuss our current understanding of the role that metallicity plays in the production of LGRBs.

  5. Low latency search for Gravitational waves from BH-NS binaries in coincidence with Short Gamma Ray Bursts

    E-Print Network [OSTI]

    Andrea Maselli; Valeria Ferrari

    2014-02-24T23:59:59.000Z

    We propose a procedure to be used in the search for gravitational waves from black hole-neutron star coalescing binaries, in coincidence with short gamma-ray bursts. It is based on two recently proposed semi-analytic fits, one reproducing the mass of the remnant disk surrounding the black hole which forms after the merging as a function of some binary parameters, the second relating the neutron star compactness, i.e. the ratio of mass and radius, with its tidal deformability. Using a Fisher matrix analysis and the two fits, we assign a probability that the emitted gravitational signal is associated to the formation of an accreting disk massive enough to supply the energy needed to power a short gamma ray burst. This information can be used in low-latency data analysis to restrict the parameter space searching for gravitational wave signals in coincidence with short gamma-ray bursts, and to gain information on the dynamics of the coalescing system and on the internal structure of the components. In addition, when the binary parameters will be measured with high accuracy, it will be possible to use this information to trigger the search for off-axis gamma-ray bursts afterglows.

  6. AN EM APPROACH TO MINERAL ANALYSIS USING NATURAL GAMMA RAYS

    E-Print Network [OSTI]

    Huynh, Du

    Engineering The University of Western Australia, Australia cScantech, Camden Park SA 5038, Australia Abstract and Electronic Engineering The University of Melbourne, Australia bSchool of Computer Science and Software-channel analyzer, which sorts the measured gamma rays into a 1024 channel spectrum by energy. For a coal

  7. Constraints on relativity violations from gamma-ray bursts

    E-Print Network [OSTI]

    Alan Kostelecky; Matthew Mewes

    2013-01-23T23:59:59.000Z

    Tiny violations of the Lorentz symmetry of relativity and the associated discrete CPT symmetry could emerge in a consistent theory of quantum gravity such as string theory. Recent evidence for linear polarization in gamma-ray bursts improves existing sensitivities to Lorentz and CPT violation involving photons by factors ranging from ten to a million.

  8. Constraining axion by polarized prompt emission from gamma ray bursts

    E-Print Network [OSTI]

    A. Rubbia; A. S. Sakharov

    2007-08-21T23:59:59.000Z

    A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of invisible axion. The axionic induced dichroism of gamma rays at different energies should cause a misalignment of the polarization plane for higher energy events relative to that one for lower energies events resulting in the loss of statistics needed to form a pattern of the polarization signal to be recognized in a detector. According to this, any evidence of polarized gamma rays coming from an object with extended magnetic field could be interpreted as a constraint on the existence of the invisible axion for a certain parameter range. Based on reports of polarized MeV emission detected in several GRBs we derive a constraint on the axion-photon coupling. This constraint $\\g_{a\\gamma\\gamma}\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the axion mass $m_a=10^{-3} {\\rm eV}$ is competitive with the sensitivity of CAST and becomes even stronger for lower masses.

  9. X- and Gamma-Ray Flashes from Type Ia Supernovae?

    E-Print Network [OSTI]

    Hoflich, Peter

    2009-01-01T23:59:59.000Z

    We investigate two potential mechanisms that will produce X-ray and gamma-ray flashes from Type Ia supernovae (SN-Ia). The mechanisms are the breakout of the thermonuclear burning front as it reaches the surface of the white dwarf and the interaction of the rapidly expanding envelope with an accretion disk. Based on the delayed-detonation scenario and detailed radiation-hydro calculation which include nuclear networks, we find that both mechanisms produce ~1 second flashes of high energy radiation with peak luminosities of 10^48 to 10^50 erg/sec with fast rises and exponential declines. The X- and gamma-ray visibility of a SN-Ia will depend strongly on self absorption within the progenitor system, specifically on the properties of the accretion disk and its orientation towards the observer. Such X-ray and gamma-ray flashes could be detected as triggered events by Gamma-Ray Burst (GRB) detectors on satellites, with events in current GRB catalogs. We have searched through the GRB catalogs (for the BATSE, HETE, ...

  10. Current Trends in Gamma Ray Detection for Radiological Emergency Response

    SciTech Connect (OSTI)

    Mukhopadhyay, S., Guss, P., Maurer, R.

    2011-08-18T23:59:59.000Z

    Passive and active detection of gamma rays from shielded radioactive materials, including special nuclear materials, is an important task for any radiological emergency response organization. This article reports on the current trends and status of gamma radiation detection objectives and measurement techniques as applied to nonproliferation and radiological emergencies.

  11. Gamma Rays from Superheavy Relic Particles in the Halo

    E-Print Network [OSTI]

    Pasquale Blasi

    1999-05-15T23:59:59.000Z

    Superheavy (SH) quasistable particles generated in the Early Universe could be responsable for Ultra High Energy Cosmic Rays (UHECR) and be a component of Cold Dark Matter (CDM) in the universe. These particles are likely to cluster in the galactic halo, so that the main part of UHECR are gamma rays produced in the decay of neutral pions. Charged pions are also produced in the same process and result in high energy electrons. We consider here the production of gamma rays by synchrotron emission of these electrons in the galactic magnetic field. The gamma ray fluxes are in the region of interest for some current and proposed experiments (e.g. EGRET, GLAST, MILAGRO) in the energy range $0.1-10^4$ GeV. A comparison with the existing upper limits at $10^5-10^8$ GeV is also carried out. The detection of this flux of gamma rays would be an important signature of SH relic particles as sources of UHECR and would give a clue to the physics of the Early Universe.

  12. A Plasma Instability Theory of Gamma-Ray Burst Emission

    E-Print Network [OSTI]

    J. J. Brainerd

    1999-04-02T23:59:59.000Z

    A plasma instability theory is presented for the prompt radiation from gamma-ray bursts. In the theory, a highly relativistic shell interacts with the interstellar medium through the filamentation and the two-stream instabilities to convert bulk kinetic energy into electron thermal energy and magnetic field energy. The processes are not efficient enough to satisfy the Rankine-Hugoniot conditions, so a shock cannot form through this mechanism. Instead, the interstellar medium passes through the shell, with the electrons radiating during this passage. Gamma-rays are produced by synchrotron self-Compton emission. Prompt optical emission is also produced through this mechanism, while prompt radio emission is produced through synchrotron emission. The model timescales are consistent with the shortest burst timescales. To emit gamma-rays, the shell's bulk Lorentz factor must be greater than approximately 1000. For the radiative processes to be efficient, the interstellar medium density must satisfy a lower limit that is a function of the bulk Lorentz factor. Because the limits operate as selection effects, bursts that violate them constitute new classes. In particular, a class of optical and ultraviolet bursts with no gamma-ray emission should exist. The lower limit on the density of the interstellar medium is consistent with the requirements of the Compton attenuation theory, providing an explanation for why all burst spectra appear to be attenuated. Several tests of the theory are discussed, as are the next theoretical investigations that should be conducted.

  13. Applications of Likelihood Analysis in Gamma-Ray Astrophysics

    E-Print Network [OSTI]

    W. F. Tompkins

    2002-02-06T23:59:59.000Z

    The field of gamma ray astronomy relies heavily on the statistical analysis of data. Because of the paucity of data, and the often large errors associated with detecting gamma rays, analysis and interpretation of the data require sophisticated statistical techniques. Techniques for extending the currently used maximum likelihood technique to more complicated data sets are presented. Similarly presented are methods of calculating the distribution and behavior of the maximum likelihood statistic used to measure source significance. A new method for calculating source variability is also proposed, and used to examine the sources found by the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory (CGRO). The results show that the Active Galactic Nuclei (AGN), pulsars, and unidentified sources have markedly different variability, and that the unidentified sources fall into at least two classes, differing in variability and spatial distribution. A class composed of possible Supernova Remnant associations (SNR) is distinctly more variable than the pulsars, but has a variability consistent with that of the other low latitude unidentified sources. Finally, the results of the Fall 1997 GLAST prototype beam test are presented. The results of the beam test are compared with simulated results, and found to be in remarkably good agreement.

  14. Gamma Ray Bursts as Probes of the First Stars

    E-Print Network [OSTI]

    James E. Rhoads

    2001-11-01T23:59:59.000Z

    The redshift where the first stars formed is an important and unknown milestone in cosmological structure formation. The evidence linking gamma ray bursts (GRBs) with star formation activity implies that the first GRBs occurred shortly after the first stars formed. Gamma ray bursts and their afterglows may thus offer a unique probe of this epoch, because they are bright from gamma ray to radio wavelengths and should be observable to very high redshift. Indeed, our ongoing near-IR followup programs already have the potential to detect bursts at redshift z ~ 10. In these proceedings, we discuss two distinct ways of using GRBs to probe the earliest star formation. First, direct GRB counts may be used as a proxy for star formation rate measurements. Second, high energy cutoffs in the GeV spectra of gamma ray bursts due to pair production with high redshift optical and ultraviolet background photons contain information on early star formation history. The second method is observationally more demanding, but also more rewarding, because each observed pair creation cutoff in a high redshift GRB spectrum will tell us about the integrated star formation history prior to the GRB redshift.

  15. airborne gamma ray: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    airborne gamma ray First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Digital Logarithmic Airborne Gamma...

  16. X-ray Spectral Properties of Gamma-Ray Bursts

    E-Print Network [OSTI]

    T. E. Strohmayer; E. E. Fenimore; T. Murakami; A. Yoshida

    1997-12-18T23:59:59.000Z

    We summarize the spectral characteristics of a sample of 22 bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide sensitivity to photons in the 2 - 400 keV range, providing a unique opportunity to characterize the largely unexplored X-ray properties of gamma-ray bursts. The photon spectra of the Ginga bursts are well described by a low energy slope, a bend energy, and a high energy slope. In the energy range where they can be compared, this result is consistent with burst spectral analyses obtained from the BATSE experiment aboard the Compton Observatory. However, below 20 keV we find evidence for a positive spectral number index in approximately 40% of our burst sample, with some evidence for a strong rolloff at lower energies in a few events. There is a correlation (Pearson's r = -0.62) between the low energy slope and the bend energy. We find that the distribution of spectral bend energies extends below 10 keV. The observed ratio of energy emitted in the X-rays relative to the gamma-rays can be much larger than a few percent and, in fact, is sometimes larger than unity. The average for our sample is 24%.

  17. Gamma-ray Bursts and their Central Engines

    E-Print Network [OSTI]

    Stephan Rosswog

    2004-01-09T23:59:59.000Z

    Gamma-ray bursts are the most luminous and probably the most relativistic events in the universe. The last few years have seen a tremendous increase in our knowledge of these events, but the source of the bursts still remains elusive. I will summarise recent progress in this field with special emphasis on our understanding of the possible progenitor systems.

  18. absolute gamma ray: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    absolute gamma ray First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Absolute Branching Ratio of...

  19. advanced gamma ray: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    gamma ray First Page Previous Page 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Next Page Last Page Topic Index 1 Pixelized Gas Micro-well Detectors for...

  20. Gamma-Ray Bursts from Neutron Star Mergers

    E-Print Network [OSTI]

    T. Piran

    1994-01-17T23:59:59.000Z

    Binary neutron stars merger (NS$^2$M) at cosmological distances is probably the only $\\gamma$-ray bursts model based on an independently observed phenomenon which is known to be taking place at a comparable rate. We describe this model, its predictions and some open questions.

  1. A Gamma-Ray Burst Bibliography, 1973-2001

    E-Print Network [OSTI]

    K. Hurley

    2002-01-18T23:59:59.000Z

    On the average, 1.5 new publications on cosmic gamma-ray bursts enter the literature every day. The total number now exceeds 5300. I describe here a relatively complete bibliography which is on the web, and which can be made available electronically in various formats.

  2. The HAWC Gamma-Ray Observatory: Design, Calibration, and Operation

    E-Print Network [OSTI]

    Abeysekara, A U; Alvarez, C; Álvarez, J D; Arceo, R; Arteaga-Velázquez, J C; Solares, H A Ayala; Barber, A S; Baughman, B M; Bautista-Elivar, N; Belmont, E; BenZvi, S Y; Berley, D; Rosales, M Bonilla; Braun, J; Caballero-Lopez, R A; Caballero-Mora, K S; Carramińana, A; Castillo, M; Cotti, U; Cotzomi, J; de la Fuente, E; De León, C; DeYoung, T; Hernandez, R Diaz; Díaz-Vélez, J C; Dingus, B L; DuVernois, M A; Ellsworth, R W; Fernandez, A; Fiorino, D W; Fraija, N; Galindo, A; Garfias, F; González, L X; González, M M; Goodman, J A; Grabski, V; Gussert, M; Hampel-Arias, Z; Hui, C M; Hüntemeyer, P; Imran, A; Iriarte, A; Karn, P; Kieda, D; Kunde, G J; Lara, A; Lauer, R J; Lee, W H; Lennarz, D; Vargas, H León; Linares, E C; Linnemann, J T; Longo, M; Luna-GarcIa, R; Marinelli, A; Martinez, H; Martinez, O; Martínez-Castro, J; Matthews, J A J; Miranda-Romagnoli, P; Moreno, E; Mostafá, M; Nava, J; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T; Patricelli, B; Pelayo, R; Pérez-Pérez, E G; Pretz, J; Rivičre, C; Rosa-González, D; Salazar, H; Salesa, F; Sanchez, F E; Sandoval, A; Santos, E; Schneider, M; Silich, S; Sinnis, G; Smith, A J; Sparks, K; Springer, R W; Taboada, I; Toale, P A; Tollefson, K; Torres, I; Ukwatta, T N; Villaseńor, L; Weisgarber, T; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Younk, P W; Zaborov, D; Zepeda, A; Zhou, H

    2013-01-01T23:59:59.000Z

    The High-Altitude Water Cherenkov Gamma Ray Observatory (HAWC) is under construction 4100 meters above sea level at Sierra Negra, Mexico. We describe the design and cabling of the detector, the characterization of the photomultipliers, and the timing calibration system. We also outline a next-generation detector based on the water Cherenkov technique.

  3. Gamma-ray probes of dark matter substructure

    SciTech Connect (OSTI)

    Campbell, Sheldon [Department of Physics and Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210 (United States)

    2014-06-24T23:59:59.000Z

    The substructure content of dark matter halos is interesting because it can be affected by complex galaxy physics and dark matter particle physics. However, observing the small scale structure of dark matter is a challenge. The subhalo abundance (mass function, minimum mass) and morphology (density profile, subhalo shape, subsubstructure) contain information about complex astrophysics (halo formation processes) and new exotic fundamental physics (dark matter interactions). Indirect detection of dark matter annihilation radiation (DMAR) in gamma rays may be the most direct method for observing small scale structure. I outline the ways in which gamma rays may probe halo substructure. If substructure is bountiful, it may be responsible for the eventual discovery of DMAR, for instance in galaxy clusters or the diffuse gamma-ray background. Otherwise, the observation of DMAR in places without much substructure, such as the Galactic center, would lead to strict limits on the properties of small scale structure. Properties of the gamma-ray angular power spectrum will also provide information or constraints on Milky Way halo substructure.

  4. Snapshot Identification of Gamma Ray Burst Optical Afterglows

    E-Print Network [OSTI]

    James E. Rhoads

    2001-04-18T23:59:59.000Z

    Gamma ray burst afterglows can be identified in single epoch observations using three or more optical filters. This method relies on color measurements to distinguish the power law spectrum of an afterglow from the curved spectra of stars. Observations in a fourth filter will further distinguish between afterglows and most galaxies up to redshifts z ~ 1. Many afterglows can also be identified with fewer filters using ultraviolet excess, infrared excess, or Lyman break techniques. By allowing faster identification of gamma ray burst afterglows, these color methods will increase the fraction of bursts for which optical spectroscopy and other narrow-field observations can be obtained. Because quasar colors can match those of afterglows, the maximum error box size where an unambiguous identification can be expected is set by the flux limit of the afterglow search and the quasar number-flux relation. For currently typical error boxes (10 -- 100 square arcminutes), little contamination is expected at magnitudes R < 21.5 +- 0.5. Archival data demonstrates that the afterglow of GRB 000301C could have been identified using this method. In addition to finding gamma ray burst counterparts, this method will have applications in ``orphan afterglow'' searches used to constrain gamma ray burst collimation.

  5. INVERSE-COMPTON CONTRIBUTION TO THE STAR-FORMING EXTRAGALACTIC GAMMA-RAY BACKGROUND

    SciTech Connect (OSTI)

    Chakraborty, Nachiketa [Department of Astronomy, University of Illinois, Urbana, IL (United States); Fields, Brian D. [Also, Department of Physics, University of Illinois, Urbana, IL (United States)

    2013-08-20T23:59:59.000Z

    Fermi has resolved several star-forming galaxies, but the vast majority of the star-forming universe is unresolved, and thus contributes to the extragalactic gamma-ray background (EGB). Here, we calculate the contribution of star-forming galaxies to the EGB in the Fermi range from 100 MeV to 100 GeV due to inverse-Compton (IC) scattering of the interstellar photon field by cosmic-ray electrons. We first construct one-zone models for individual star-forming galaxies assuming that supernovae power the acceleration of cosmic rays. We develop templates for both normal and starburst galaxies, accounting for differences in the cosmic-ray electron propagation and in the interstellar radiation fields. For both types of star-forming galaxies, the same IC interactions leading to gamma rays also substantially contribute to the energy loss of the high-energy cosmic-ray electrons. Consequently, a galaxy's IC emission is determined by the relative importance of IC losses in the cosmic-ray electron energy budget ({sup p}artial calorimetry{sup )}. We calculate the cosmological contribution of star-forming galaxies to the EGB using our templates and the cosmic star formation rate distribution. For all of our models, we find that the IC EGB contribution is almost an order of magnitude less than the peak of the emission due to cosmic-ray ion interactions (mostly pionic p{sub cr} p{sub ism} {yields} {pi}{sup 0} {yields} {gamma}{gamma}); even at the highest Fermi energies, IC is subdominant. The flatter IC spectrum increases the high-energy signal of the pionic+IC sum, bringing it closer to the EGB spectral index observed by Fermi. Partial calorimetry ensures that the overall IC signal is relatively well constrained, with only uncertainties in the amplitude and spectral shape for plausible model choices. We conclude with a brief discussion on how the pionic spectral feature and other methods can be used to measure the star-forming component of the EGB.

  6. Selected Results from Ground-Based Cosmic Ray and Gamma-Ray Experiments

    E-Print Network [OSTI]

    N. Magnussen

    1998-05-13T23:59:59.000Z

    Selected results from the HEGRA experiment on charged Cosmic Rays and on very high energy gamma-rays are presented. The MAGIC Telescope is presented as an outlook to the future of Gamma-Ray astronomy.

  7. Investigation of elemental analysis using neutron-capture gamma ray spectra

    E-Print Network [OSTI]

    Hamawi, John Nicholas

    1969-01-01T23:59:59.000Z

    This thesis evaluated the potential of neutron-capture gamma rays in elemental analysis. A large portion of the work was devoted to the development of a method for the analysis of weak peaks in gamma ray spectra. This was ...

  8. THE INTERPLANETARY NETWORK SUPPLEMENT TO THE HETE-2 GAMMA-RAY BURST CATALOG

    E-Print Network [OSTI]

    Vanderspek, Roland K.

    Between 2000 November and 2006 May, one or more spacecraft of the interplanetary network (IPN) detected 226 cosmic gamma-ray bursts that were also detected by the French Gamma-Ray Telescope experiment on board the High ...

  9. 1 Cactus Framework: Black Holes to Gamma Ray Bursts 7 Erik Schnetter1,2

    E-Print Network [OSTI]

    Contents 1 Cactus Framework: Black Holes to Gamma Ray Bursts 7 Erik Schnetter1,2 , Christian D. Ott 94720, USA 1.1 Current challenges in relativistic astrophysics and the Gamma- Ray Burst problem

  10. Search for Prompt Neutrino Emission from Gamma-Ray Bursts with IceCube

    E-Print Network [OSTI]

    Aartsen, M G; Adams, J; Aguilar, J A; Ahlers, M; Ahrens, M; Altmann, D; Anderson, T; Arguelles, C; Arlen, T C; Auffenberg, J; Bai, X; Barwick, S W; Baum, V; Bay, R; Beatty, J J; Tjus, J Becker; Becker, K -H; BenZvi, S; Berghaus, P; Berley, D; Bernardini, E; Bernhard, A; Besson, D Z; Binder, G; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohm, C; Bos, F; Bose, D; Böser, S; Botner, O; Brayeur, L; Bretz, H -P; Brown, A M; Buzinsky, N; Casey, J; Casier, M; Cheung, E; Chirkin, D; Christov, A; Christy, B; Clark, K; Classen, L; Clevermann, F; Coenders, S; Cowen, D F; Silva, A H Cruz; Daughhetee, J; Davis, J C; Day, M; de André, J P A M; De Clercq, C; De Ridder, S; Desiati, P; de Vries, K D; de With, M; DeYoung, T; Díaz-Vélez, J C; Dunkman, M; Eagan, R; Eberhardt, B; Ehrhardt, T; Eichmann, B; Eisch, J; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Felde, J; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Frantzen, K; Fuchs, T; Gaisser, T K; Gaior, R; Gallagher, J; Gerhardt, L; Gier, D; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Golup, G; Gonzalez, J G; Goodman, J A; Góra, D; Grant, D; Gretskov, P; Groh, J C; Groß, A; Ha, C; Haack, C; Ismail, A Haj; Hallen, P; Hallgren, A; Halzen, F; Hanson, K; Hebecker, D; Heereman, D; Heinen, D; Helbing, K; Hellauer, R; Hellwig, D; Hickford, S; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huang, F; Huelsnitz, W; Hulth, P O; Hultqvist, K; Ishihara, A; Jacobi, E; Jacobsen, J; Japaridze, G S; Jero, K; Jlelati, O; Jurkovic, M; Kaminsky, B; Kappes, A; Karg, T; Karle, A; Kauer, M; Keivani, A; Kelley, J L; Kheirandish, A; Kiryluk, J; Kläs, J; Klein, S R; Köhne, J -H; Kohnen, G; Kolanoski, H; Koob, A; Köpke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Kriesten, A; Krings, K; Kroll, G; Kroll, M; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Lanfranchi, J L; Larsen, D T; Larson, M J; Lesiak-Bzdak, M; Leuermann, M; Lünemann, J; Madsen, J; Maggi, G; Maruyama, R; Mase, K; Matis, H S; Maunu, R; McNally, F; Meagher, K; Medici, M; Meli, A; Meures, T; Miarecki, S; Middell, E; Middlemas, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Nahnhauer, R; Naumann, U; Niederhausen, H; Nowicki, S C; Nygren, D R; Obertacke, A; Odrowski, S; Olivas, A; Omairat, A; O'Murchadha, A; Palczewski, T; Paul, L; Penek, Ö; Pepper, J A; Heros, C Pérez de los; Pfendner, C; Pieloth, D; Pinat, E; Posselt, J; Price, P B; Przybylski, G T; Pütz, J; Quinnan, M; Rädel, L; Rameez, M; Rawlins, K; Redl, P; Rees, I; Reimann, R; Relich, M; Resconi, E; Rhode, W; Richman, M; Riedel, B; Robertson, S; Rodrigues, J P; Rongen, M; Rott, C; Ruhe, T; Ruzybayev, B; Ryckbosch, D; Saba, S M; Sander, H -G; Sandroos, J; Santander, M; Sarkar, S; Schatto, K; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schöneberg, S; Schönwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Sestayo, Y; Seunarine, S; Shanidze, R; Smith, M W E; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stanisha, N A; Stasik, A; Stezelberger, T; Stokstad, R G; Stößl, A; Strahler, E A; Ström, R; Strotjohann, N L; Sullivan, G W; Taavola, H; Taboada, I; Tamburro, A; Tepe, A; Ter-Antonyan, S; Terliuk, A; Teši?, G; Tilav, S; Toale, P A; Tobin, M N; Tosi, D; Tselengidou, M; Unger, E; Usner, M; Vallecorsa, S; van Eijndhoven, N; Vandenbroucke, J; van Santen, J; Vanheule, S; Vehring, M; Voge, M; Vraeghe, M; Walck, C; Wallraff, M; Weaver, Ch; Wellons, M; Wendt, C; Westerhoff, S; Whelan, B J; Whitehorn, N; Wichary, C; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, D L; Xu, X W; Xu, Y; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zoll, M

    2014-01-01T23:59:59.000Z

    We present constraints derived from a search of four years of IceCube data for a prompt neutrino flux from gamma-ray bursts (GRBs). A single low-significance neutrino was found in coincidence with one of the 506 observed bursts, consistent with the expectation from atmospheric backgrounds. Although GRBs have been proposed as candidate sources for ultra-high energy cosmic rays, our limits on the neutrino flux disfavor much of the parameter space for the latest models. We also find that no more than $\\sim1\\%$ of the recently observed astrophysical neutrino flux consists of prompt emission from GRBs that are potentially observable by existing satellites.

  11. A search for GeV-TeV emission from Gamma-ray Bursts using the Milagro detector

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    A search for GeV-TeV emission from Gamma-ray Bursts using the Milagro detector p. M. Saz Parkinson of operation. Keywords: gamma-ray sources; gamma-ray bursts; astronomical observations gamma-ray; gamma-ray telescope; Milagro PACS: 95.55.Ka; 95.85.Pw; 98.70.Rz INTRODUCTION Gamma-ray bursts (GRBs) were detected up

  12. Sub-TeV Gamma-Ray Astrophysics using Large Air Cerenkov Toru Tanimori3)

    E-Print Network [OSTI]

    Enomoto, Ryoji

    detection of persistent TeV gamma-ray emission from the Crab in 1989, several type of TeV gamma-ray sources the huge black holes at the center of galaxies. Recent detections of TeV gamma- ray emission from several+514, SN1006 Fig. 2. GeV gamma-ray source catalog detected by EGRET in galactic coordinates, where six Te

  13. SubTeV GammaRay Astrophysics using Large Air Toru Tanimori 3)

    E-Print Network [OSTI]

    Enomoto, Ryoji

    detection of persistent TeV gamma­ray emission from the Crab in 1989, several type of TeV gamma­ray sources the huge black holes at the center of galaxies. Recent detections of TeV gamma­ ray emission from severalES2344+514, SN1006 Fig. 2. GeV gamma­ray source catalog detected by EGRET in galactic coordinates

  14. Relativistic Winds from Compact Gamma-Ray Sources: II. Pair Loading and Radiative Acceleration in Gamma-ray Bursts

    E-Print Network [OSTI]

    Christopher Thompson; Piero Madau

    2000-02-21T23:59:59.000Z

    We consider the effects of rapid pair creation by an intense pulse of gamma-rays propagating ahead of a relativistic shock. Side-scattered photons colliding with the main gamma-ray beam amplify the density of scattering charges. The acceleration rate of the pair-loaded medium is calculated, and its limiting bulk Lorentz factor related to the spectrum and compactness of the photon source. One obtains, as a result, a definite prediction for the relative inertia in baryons and pairs. The deceleration of a relativistic shock in the moving medium, and the resulting synchrotron emissivity, are compared with existing calculations for a static medium. The radiative efficiency is increased dramatically by pair loading. When the initial ambient density exceeds a critical value, the scattering depth traversed by the main gamma-ray pulse rises above unity, and the pulse is broadened. These considerations place significant constraints on burst progenitors: a pre-burst mass loss rate exceeding 10^{-5} M_\\odot per year is difficult to reconcile with individual pulses narrower than 10 s, unless the radiative efficiency is low. An anisotropic gamma-ray flux (on an angular scale \\Gamma^{-1} or larger) drives a large velocity shear that greatly increases the energy in the seed magnetic field forward of the propagating shock.

  15. Agile Detection of Delayed Gamma-Ray Emission from the Short Gamma-Ray Burst GRB 090510

    E-Print Network [OSTI]

    Giuliani, A; Vianello, G; Marisaldi, M; Mereghetti, S; Tavani, M; Cutini, S; Barbiellini, G; Longo, F; Moretti, E; Feroci, M; Del Monte, E; Argan, A; Bulgarelli, A; Caraveo, P; Cattaneo, P W; Chen, A W; Contessi, T; D'Ammando, F; Costa, E; De Paris, G; Di Cocco, G; Donnarumma, I; Evangelista, Y; Ferrari, A; Fiorini, M; Galli, M; Gianotti, F; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Morselli, A; Pacciani, L; Pellizzoni, A; Perotti, F; Piano, G; Picozza, P; Pilia, M; Pucella, G; Prest, M; Rapisarda, M; Rappoldi, A; Rubini, A; Sabatini, S; Scalise, E; Striani, E; Soffitta, P; Trifoglio, M; Trois, A; Vallazza, E; Vercellone, S; Vittorini, V; Zambra, A; Zanello, D; Pittori, C; Verrecchia, F; Santolamazza, P; Giommi, P; Colafrancesco, S; Antonelli, L A; Salotti, L

    2009-01-01T23:59:59.000Z

    Short gamma-ray bursts (GRBs), typically lasting less than 2 s, are a special class of GRBs of great interest. We report the detection by the AGILE satellite of the short GRB 090510 which shows two clearly distinct emission phases: a prompt phase lasting ~ 200 msec and a second phase lasting tens of seconds. The burst is relatively intense in the 0.3-10 MeV range showing a spectrum of the prompt phase characterized by a large peak/cutoff energy near 3 MeV. Following the prompt phase, gamma-ray photons above 30 MeV were detected showing a power-law time decay of the flux of the type t^-1.3. The broad-band spectrum of this "delayed gamma-ray emission phase" is remarkably different from that of the prompt phase. It extends from sub-MeV to hundreds of MeV energies with a photon index alpha ~ 1.5. We present the timing and spectral data of GRB 090510 and briefly discuss its remarkable properties within the current models of gamma-ray emission of short GRBs.

  16. Characteristics of broadband lightning emissions associated with terrestrial gamma ray flashes

    E-Print Network [OSTI]

    Cummer, Steven A.

    . Introduction [2] Brief (typically bursts of gamma rays with mean energies of 2 MeV originating from the Earth's atmosphere, referred to as terrestrial gamma ray flashes (TGFs), have been observed by the Burst et al., 2010; Briggs et al., 2010]. With spectra typically harder than cosmic gamma ray bursts

  17. EFFECT OF IRRADIATION (GAMMA RAYS) ON THE BIOLOGY OF EIMERIA TENELLA OOCYSTS

    E-Print Network [OSTI]

    Boyer, Edmond

    EFFECT OF IRRADIATION (GAMMA RAYS) ON THE BIOLOGY OF EIMERIA TENELLA OOCYSTS R.S. BAJWA B.S. GILL, 1932), X-rays (Alba- nese and Smetana, 1934 ; Waxler, 1941 ; Siba- lic, 1970) and gamma rays (Baldelli. acervulina (Ali et al., 1972) to gamma rays have been reported to result in decreased infectivity. Waxler

  18. Modeling and simulation results on high sensitivity scattered gamma-ray emission imaging

    E-Print Network [OSTI]

    Nguyen-Verger, Maď K.

    Modeling and simulation results on high sensitivity scattered gamma-ray emission imaging C. Driol a simulations Numerical image reconstruction a b s t r a c t A new modality in gamma-ray emission imaging, based modality in gamma-ray emission imaging with potential applications in many fields such as bio

  19. Study of Very High Energy Gamma-ray Emission from the Pulsar Wind Nebula in

    E-Print Network [OSTI]

    Enomoto, Ryoji

    telescopes have achieved remarkably high sensitivity in the very high energy gamma-ray band. This is well-wavelength spectra were per- formed, based on both leptonic and hadronic models. In the leptonic model, gamma raysStudy of Very High Energy Gamma-ray Emission from the Pulsar Wind Nebula in MSH 15-52 with CANGAROO

  20. A EUROPEAN PROPOSAL FOR THE COMPTON GAMMA-RAY SOURCE OF ELI-NP*

    E-Print Network [OSTI]

    Boyer, Edmond

    . The predicted gamma-ray spectra have been evaluated for the case at 360 MeV. INTRODUCTION In the context of Gamma-ray photons is planned, capable to produce beams of mono-chromatic and high spectral density gammaA EUROPEAN PROPOSAL FOR THE COMPTON GAMMA-RAY SOURCE OF ELI-NP* C. Vaccarezza, O. Adriani, S

  1. Constraining the Intergalactic Magnetic Field Through its Imprint on Gamma Ray Data from Distant Sources.

    E-Print Network [OSTI]

    Arlen, Timothy

    2013-01-01T23:59:59.000Z

    Energy Emission of Gamma-Ray Bursts. ” ApJ, 682:127–134,1 GeV = 10 9 eV GRB Gamma-ray burst HE High energy, 100 MeVrays”-either from gamma-ray bursts or flares from blazars

  2. TeV GAMMA RAYS FROM PLERIONS AND RESULTS OF CAN-GAROO PROJECT

    E-Print Network [OSTI]

    @icrr.u-tokyo.ac.jp ABSTRACT Ground-based detection of very high energy gamma rays at Tev energies is discussed by using production, accel- eration and interaction of energetic particles. The point-like source of gamma raysV energies gamma rays is characterized by the interactions of energetic particles. The observation window

  3. THE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT

    E-Print Network [OSTI]

    Enomoto, Ryoji

    m diameter has a threshold energy of detecting gamma rays near 100 GeV. Also discussed is the next; in the region of 100 GeV to TeV energies) gamma rays are linked to energetic particles. They are produced through the non­thermal mechanism of those elementary particles as progenitor. Gamma rays are to suffer

  4. \\NEW" OBSERVATION OF TEV GAMMA RAY SOURCES: Relation to Origin of Matter and Early Universe

    E-Print Network [OSTI]

    Enomoto, Ryoji

    with matter by interactions of el- ementary particles, and gamma ray detection veri#12;es the processes of particle acceleration taking place in bright gamma ray sources, such as AGN (active galactic nuclei that utilizes the atmosphere as a calorimeter of absorbing gamma rays has a large detection area of more than

  5. THE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT

    E-Print Network [OSTI]

    Enomoto, Ryoji

    a threshold energy of detecting gamma rays near 100 GeV. Also discussed is the next step we plan to take particles as progenitor. Gamma rays are to su er from the absorption through the pair creation of electron. Attempts to detect the relic phenomena have failed so far and remain as potential targets that gamma ray

  6. Stereo Matching and 3D Visualization for Gamma-Ray Cargo Inspection Zhigang Zhu*ab

    E-Print Network [OSTI]

    Zhu, Zhigang

    Stereo Matching and 3D Visualization for Gamma-Ray Cargo Inspection Zhigang Zhu*ab , Yu-Chi Hubc visualization issues are studied for a linear pushbroom stereo model built for 3D gamma-ray (or x-ray) cargo results are presented for real gamma-ray images of a 3D cargo container and the objects inside. The 3D

  7. The Interplanetary Network Supplement to the BATSE 5B Catalog of Cosmic Gamma-Ray Bursts

    E-Print Network [OSTI]

    California at Berkeley, University of

    The Interplanetary Network Supplement to the BATSE 5B Catalog of Cosmic Gamma-Ray Bursts K. Hurley Interplanetary Network (IPN) localization information for 343 gamma-ray bursts observed by the Burst Gamma-Ray Observatory (CGRO) mission, obtained by analyzing the arrival times of these bursts

  8. Evolution of massive Be and Oe stars at low metallicity towards the Long Gamma Ray bursts

    E-Print Network [OSTI]

    Evolution of massive Be and Oe stars at low metallicity towards the Long Gamma Ray bursts C and massive stars, and the theoretical predictions of the characteristics must have the long gamma-ray burst of that document deals with the long soft gamma ray bursts (here type 2 bursts) and their possible relationship

  9. Gamma-Ray Bursts in the Swift Era N. Gehrels,1

    E-Print Network [OSTI]

    Rodriguez, Luis F.

    1 Gamma-Ray Bursts in the Swift Era N. Gehrels,1 E. Ramirez-Ruiz,2 and D. B. Fox3 [1] NASA IS A GAMMA-RAY BURST? . . . . . . . . . . . . . . . . . . . . . . . . . 6 BURST AND AFTERGLOW OBSERVATIONS medium, high- redshift; gamma rays: observations, theory; stars: Wolf-Rayet; neutrinos; supernovae

  10. Studies of Gamma-Ray Burst Prompt Emission with RHESSI and NCT

    E-Print Network [OSTI]

    Bellm, Eric Christopher

    2011-01-01T23:59:59.000Z

    4 RHESSI Tests of Quasi-Thermal Gamma-Ray Burst Spectral 4.1List of Tables ix Acknowledgments 1 Gamma-Ray Bursts 1.1 GRBx 2 RHESSI Gamma-Ray Burst Analysis Methods 2.1 The RHESSI

  11. Milagro Search for Very High Energy Emission from Gamma-Ray Bursts in the Swift Era

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    Milagro Search for Very High Energy Emission from Gamma-Ray Bursts in the Swift Era P. M. Saz an unprecedented number of rapid and accurate Gamma-Ray Burst (GRB) localizations, facilitating a flurry of follow as the flares. INTRODUCTION Some of the most important contributions to our understanding of gamma-ray bursts

  12. GAMMA-RAY BURSTS AND THE EARTH: EXPLORATION OF ATMOSPHERIC, BIOLOGICAL, CLIMATIC, AND BIOGEOCHEMICAL EFFECTS

    E-Print Network [OSTI]

    Jackman, Charles H.

    GAMMA-RAY BURSTS AND THE EARTH: EXPLORATION OF ATMOSPHERIC, BIOLOGICAL, CLIMATIC Received 2005 May 19; accepted 2005 August 2 ABSTRACT Gamma-ray bursts (GRBs) are likely to have made extinction may have been initiated by a GRB. Subject headinggs: astrobiology -- gamma rays: bursts Online

  13. A ground level gamma-ray burst observed in association with rocket-triggered lightning

    E-Print Network [OSTI]

    Florida, University of

    A ground level gamma-ray burst observed in association with rocket-triggered lightning J. R. Dwyer 2004; published 13 March 2004. [1] We report the observation of an intense gamma-ray burst observed lightning channel with gamma-ray energies extending up to more than 10 MeV. The burst consisted of 227

  14. THE INTERPLANETARY NETWORK SUPPLEMENT TO THE BATSE CATALOGS OF UNTRIGGERED COSMIC GAMMA-RAY BURSTS

    E-Print Network [OSTI]

    California at Berkeley, University of

    THE INTERPLANETARY NETWORK SUPPLEMENT TO THE BATSE CATALOGS OF UNTRIGGERED COSMIC GAMMA-RAY BURSTS gamma-ray bursts (GRBs) observed as untriggered events by the Burst and Transient Source Experiment to detect BATSE un- triggered bursts. Subject headinggs: catalogs -- gamma rays: bursts Online material

  15. Did a gamma-ray burst initiate the late Ordovician mass extinction?

    E-Print Network [OSTI]

    Jackman, Charles H.

    Did a gamma-ray burst initiate the late Ordovician mass extinction? A.L. Melott1 , B.S. Lieberman2 Abstract: Gamma-ray bursts (GRBs) produce a flux of radiation detectable across the observable Universe words: Population and evolution, mass extinction, gamma-ray burst, Ordovician, ultraviolet ozone

  16. Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro P. M. Saz Parkinson 95064 Abstract. Gamma-Ray Bursts (GRBs) have been detected at GeV energies by EGRET and models predict for very high energy emission from a sample of 106 gamma-ray bursts (GRB) detected since the beginning

  17. Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts

    E-Print Network [OSTI]

    California at Berkeley, University of

    Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts V with short gamma ray bursts detected by the InterPlanetary Network (IPN) during LIGO's fifth science run and Virgo's first science run. The IPN localisation of short gamma ray bursts is limited to extended error

  18. SOLAR SUBMILLIMETER AND GAMMA-RAY BURST EMISSION P. Kaufmann,1,2

    E-Print Network [OSTI]

    Giménez de Castro, Guillermo Carlos

    SOLAR SUBMILLIMETER AND GAMMA-RAY BURST EMISSION P. Kaufmann,1,2 J.-P. Raulin,1 A. M. Melo,1 E headings: gamma rays: bursts -- Sun: flares 1. INTRODUCTION The interaction of ultrarelativistic electrons observations of a burst in the submillimeter and gamma-ray ranges were obtained for the first time on 2001

  19. Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    OG 2.3.07 Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope Gus for short duration bursts of TeV photons. Such bursts may result from "traditional" gamma-ray bursts to gamma-ray bursts, the final stages of black hole evaporation) the most compelling reason may

  20. Title of dissertation: A SEARCH FOR BURSTS OF VERY HIGH ENERGY GAMMA RAYS

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    ABSTRACT Title of dissertation: A SEARCH FOR BURSTS OF VERY HIGH ENERGY GAMMA RAYS WITH MILAGRO though the search was optimized primarily for detecting the emission from Gamma-Ray Bursts (GRBs) or to any other kind of phenomena that produce bursts of VHE gamma rays. Measurements of the GRB spectra

  1. arXiv:astro-ph/0509571v119Sep2005 Gamma-Ray Burst Early Afterglows

    E-Print Network [OSTI]

    Zhang, Bing

    arXiv:astro-ph/0509571v119Sep2005 Gamma-Ray Burst Early Afterglows Bing Zhang Department of Physics's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore the unknown

  2. UNIVERSITY of CALIFORNIA A SEARCH FOR TEV GAMMA-RAY BURST EMISSION WITH

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    UNIVERSITY of CALIFORNIA SANTA CRUZ A SEARCH FOR TEV GAMMA-RAY BURST EMISSION WITH THE MILAGRO of Figures vi List of Tables viii Abstract ix Dedication x Acknowledgments xi 1 Gamma-Ray Bursts 1 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.6 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 6 Gamma-Ray Burst

  3. Climatic and biogeochemical effects of a galactic gamma ray burst Adrian L. Melott,1

    E-Print Network [OSTI]

    Jackman, Charles H.

    Climatic and biogeochemical effects of a galactic gamma ray burst Adrian L. Melott,1 Brian C. Jackman (2005), Climatic and biogeochemical effects of a galactic gamma ray burst, Geophys. Res. Lett., 32, L14808, doi:10.1029/2005GL023073. 1. Terrestrial Implications of Gamma Ray Bursts in Our Galaxy [2

  4. Constraints on Particle Acceleration from the Diffuse Isotropic Gamma-Ray Background

    E-Print Network [OSTI]

    Karl Mannheim

    2000-05-26T23:59:59.000Z

    Gamma rays trace accelerated particles, and the observed flux of extragalactic gamma rays therefore constrains the global efficiency for particle acceleration. Extragalactic jets in active galactic nuclei can account for the gamma ray background if their particle acceleration efficiency considerably exceeds ~ 18 per cent which would imply that particle acceleration is an essential part of the thermodynamics in these sources.

  5. Study of galactic gamma ray sources with Milagro Jordan A. Goodman for the Milagro Collaboration

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    in the Cygnus Region [3], and the possible detection of a gamma-ray burst with our prototype instrument] and the Crab Nebula [7], set stringent upper limits on the prompt TeV emission from several gamma ray bursts [8Study of galactic gamma ray sources with Milagro Jordan A. Goodman for the Milagro Collaboration

  6. UNIVERSITY OF CALIFORNIA Search for a TeV Component of GammaRay Bursts

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    UNIVERSITY OF CALIFORNIA IRVINE Search for a TeV Component of Gamma­Ray Bursts Using the Milagrito Acknowledgements xiii Curriculum Vitae xv Abstract xvi 1. Introduction 1 2. Gamma­Ray Bursts: Observations.2 The Compton Gamma­Ray Observatory . . . . . . . . . . . . . . . . . . . 6 2.3 BATSE's Contributions

  7. Source altitudes of terrestrial gamma-ray flashes produced by lightning leaders

    E-Print Network [OSTI]

    Pasko, Victor

    ; published 18 April 2012. [1] Terrestrial gamma-ray flashes (TGFs) are energetic photon bursts observed fromSource altitudes of terrestrial gamma-ray flashes produced by lightning leaders Wei Xu,1 Sebastien. Pasko (2012), Source altitudes of terres- trial gamma-ray flashes produced by lightning leaders, Geophys

  8. Gamma Ray Astronomy with Air Shower Arrays A.I. Mincer 1

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    and for searching for transient sources such as gamma ray bursts. The Milagro detector is currently operating such as gamma ray bursts or to study the time variation of ``steady'' sources, air shower arrays are usedGamma Ray Astronomy with Air Shower Arrays A.I. Mincer 1 New York University, New York, NY 10003

  9. Limits on Very High Energy Emission from Gamma-Ray Bursts with the Milagro

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    Limits on Very High Energy Emission from Gamma-Ray Bursts with the Milagro Observatory Miguel F of Milagro allow it to detect very high energy (VHE) gamma-ray burst emission with much higher sensitivity gamma-ray burst satellites at keV to MeV energies. Even in the absence of a positive detection, VHE

  10. Fermi LAT Observations of LS 5039

    SciTech Connect (OSTI)

    Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Blandford, R.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique /Washington U., Seattle /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /NASA, Goddard /NASA, Goddard /CSST, Baltimore /DAPNIA, Saclay /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Sonoma State U. /Stockholm U. /Stockholm U., OKC /DAPNIA, Saclay /NASA, Goddard /CSST, Baltimore /SLAC /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC /Grenoble Observ. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U.; /more authors..

    2012-03-29T23:59:59.000Z

    The first results from observations of the high-mass X-ray binary LS 5039 using the Fermi Gamma-ray Space Telescope data between 2008 August and 2009 June are presented. Our results indicate variability that is consistent with the binary period, with the emission being modulated with a period of 3.903 {+-} 0.005 days; the first detection of this modulation at GeV energies. The light curve is characterized by a broad peak around superior conjunction in agreement with inverse Compton scattering models. The spectrum is represented by a power law with an exponential cutoff, yielding an overall flux (100 MeV-300 GeV) of 4.9 {+-} 0.5(stat) {+-} 1.8(syst) x 10{sup -7} photon cm{sup -2} s{sup -1}, with a cutoff at 2.1 {+-} 0.3(stat) {+-} 1.1(syst) GeV and photon index {Gamma} = 1.9 {+-} 0.1(stat) {+-} 0.3(syst). The spectrum is observed to vary with orbital phase, specifically between inferior and superior conjunction. We suggest that the presence of a cutoff in the spectrum may be indicative of magnetospheric emission similar to the emission seen in many pulsars by Fermi.

  11. Modeling of the $\\gamma$-ray pulsed spectra of Geminga, Crab, and Vela with synchro-curvature radiation

    E-Print Network [OSTI]

    Viganň, Daniele

    2015-01-01T23:59:59.000Z

    $\\gamma$-ray spectra of pulsars have been mostly studied in a phenomenological way, by fitting them to a cut-off power-law function. Here, we analyze a model where pulsed emission comes from synchro-curvature processes in a gap. We calculate the variation of kinetic energy of magnetospheric particles along the gap and the associated radiated spectra, considering an effective particle distribution. We fit the phase-averaged and phase-resolved {\\em Fermi}-LAT spectra of the three brightest $\\gamma$-ray pulsars: Geminga, Crab, and Vela, and constrain the three free parameters we leave free in the model. Our best-fit models well reproduce the observed data, apart from residuals above a few GeV in some cases, range for which the inverse Compton scattering likely becomes the dominant mechanism. In any case, the flat slope at low-energy ($\\lesssim$ GeV) seen by {\\it Fermi}-LAT both in the phase-averaged and phase-resolved spectra of most pulsars, including the ones we studied, requires that most of the detected radi...

  12. Star-forming galaxies as the origin of diffuse high-energy backgrounds: Gamma-ray and neutrino connections, and implications for starburst history

    E-Print Network [OSTI]

    Irene Tamborra; Shin'ichiro Ando; Kohta Murase

    2014-08-29T23:59:59.000Z

    Star-forming galaxies have been predicted to contribute considerably to the diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Assuming that the hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos and that O(100) PeV cosmic rays can be produced and confined in starburst galaxies, we here discuss the possibility that star-forming galaxies are also the main sources of the high-energy neutrinos observed by the IceCube experiment. First, we compute the diffuse gamma-ray background from star-forming galaxies, adopting the latest Herschel PEP/HerMES luminosity function and relying on the correlation between the gamma-ray and infrared luminosities reported by Fermi observations. Then we derive the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies including normal and starburst galaxies. Our results indicate that starbursts, including those with active galactic nuclei and galaxy mergers, could be the main sources of the high-energy neutrinos observed by the IceCube experiment. We find that assuming a cosmic-ray spectral index of 2.1-2.2 for all starburst-like galaxies, our predictions can be consistent with both the Fermi and IceCube data, but larger indices readily fail to explain the observed diffuse neutrino flux. Taking the starburst high-energy spectral index as free parameter, and extrapolating from GeV to PeV energies, we find that the spectra harder than E^(-2.15) are likely to be excluded by the IceCube data, which can be more constraining than the Fermi data for this population.

  13. HAWC: A Next Generation All-Sky VHE Gamma-Ray Telescope

    E-Print Network [OSTI]

    G. Sinnis; A. Smith; J. E. McEnery

    2004-03-03T23:59:59.000Z

    The study of the universe at energies above 100 GeV is a relatively new and exciting field. The current generation of pointed instruments have detected TeV gamma rays from at least 10 sources and the next generation of detectors promises a large increase in sensitivity. We have also seen the development of a new type of all-sky monitor in this energy regime based on water Cherenkov technology (Milagro). To fully understand the universe at these extreme energies requires a highly sensitive detector capable of continuously monitoring the entire overhead sky. Such an instrument could observe prompt emission from gamma-ray bursts and probe the limits of Lorentz invariance at high energies. With sufficient sensitivity it could detect short transients ($\\sim$15 minutes) from active galaxies and study the time structure of flares at energies unattainable to space-based instruments. Unlike pointed instruments a wide-field instrument can make an unbiased study of all active galaxies and enable many multi-wavelength campaigns to study these objects. This paper describes the design and performance of a next generation water Cherenkov detector. To attain a low energy threshold and have high sensitivity the detector should be located at high altitude ($>$ 4km) and have a large area ($\\sim$40,000 m$^2$). Such an instrument could detect gamma ray bursts out to a redshift of 1, observe flares from active galaxies as short as 15 minutes in duration, and survey the overhead sky at a level of 50 mCrab in one year.

  14. Fresnel lenses for X-ray and Gamma-ray Astronomy

    E-Print Network [OSTI]

    Gerry Skinner; Peter von Ballmoos; Neil Gehrels; John Krizmanic

    2003-08-25T23:59:59.000Z

    Phase Fresnel lenses have the same imaging properties as zone plates, but with the possibility of concentrating all of the incident power into the primary focus, increasing the maximum theoretical efficiency from 11% to close to 100%. For X-rays, and in particular for gamma-rays, large, diffraction-limited phase Fresnel lenses can be made relatively easily. The focal length is very long - for example up to a million kms. However, the correspondingly high `plate-scale' of the image means that the ultra-high (sub-micro-arc-second) angular resolution possible with a diffraction limited gamma-ray lens a few metres in diameter can be exploited with detectors having \\~mm spatial resolution. The potential of such systems for ultra-high angular resolution astronomy, and for attaining the sensitivity improvements desperately needed for certain other studies, are reviewed and the advantages and disadvantages vis-a-vis alternative approaches are discussed. We report on reduced-scale 'proof-of-principle tests' which are planned and on mission studies of the implementation of a Fresnel telescope on a space mission with lens and detector on two spacecraft separated by one million km. Such a telescope would be capable of resolving emission from super-massive black holes on the scale of their event horizons and would have the sensitivity necessary to detect gamma-ray lines from distant supernovae. We show how diffractive/refractive optics leads to a continuum of possible system designs between filled aperture lenses and wideband interferometric arrays.

  15. HAWC: a next generation all-sky VHE gamma-ray telescope

    SciTech Connect (OSTI)

    Sinnis, G. (Gus); Smith, A.; McEnery, J. E.

    2004-01-01T23:59:59.000Z

    The study of the universe at energies above 100 GeV is a relatively new and exciting field. The current generation of pointed instruments have detected TeV gamma rays from at least 10 sources and the next generation of detectors promises a large increase in sensitivity. We have also seen the development of a new type of all-sky monitor in this energy regime based on water Cherenkov technology (Milagro). To fully understand the universe at these extreme energies requires a highly sensitive detector capable of continuously monitoring the entire overhead sky. Such an instrument could observe prompt emission from gamma-ray bursts and probe the limits of Lorentz invariance at high energies. With sufficient sensitivity it could detect shorthransients ({approx}15 minutes) from active galaxies and study the time structure of flares at energies unattainable to space-based instruments. Unlike pointed instruments a wide-field instrument can make an unbiased study of all active galaxies and enable many multi-wavelength campaigns to study these objects. This paper describes the design and performance of a next generation water Cherenkov detector. To attain a low energy threshold and have high sensitivity the detector should be located at high altitude (> 4km) and have a large area ({approx}40,000 m{sup 2}). Such an instrument could detect gamma ray bursts out to a redshift of 1, observe flares from active galaxies as short as 15 minutes in duration, and survey the overhead sky at a level of 50 mCrab in one year.

  16. Polarimetric performance of a Laue lens gamma-ray CdZnTe focal plane prototype

    SciTech Connect (OSTI)

    Curado da Silva, R. M. [Departmento de Fisica, Universidade de Coimbra, P-3000 Coimbra (Portugal); Center for Space Radiations, Univesite Catholique de Louvain (Belgium); Caroli, E.; Stephen, J. B.; Schiavone, F.; Donati, A.; Ventura, G. [Istituto di Astrofisica Spaziale e Fisica Cosmica-Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Pisa, A.; Auricchio, N.; Frontera, F. [Dipartimento di Fisica, Universita di Ferrara, Ferrara (Italy); Del Sordo, S. [Istituto di Astrofisica Spaziale e Fisica Cosmica-Palermo, Via Ugo La Malfa 153, 90146 Palermo (Italy); Honkimaeki, V. [European Synchrotron Radiation Facility, Grenoble (France); Trindade, A. M. F. [Departmento de Fisica, Universidade de Coimbra, P-3000 Coimbra (Portugal)

    2008-10-15T23:59:59.000Z

    A gamma-ray telescope mission concept [gamma ray imager (GRI)] based on Laue focusing techniques has been proposed in reply to the European Space Agency call for mission ideas within the framework of the next decade planning (Cosmic Vision 2015-2025). In order to optimize the design of a focal plane for this satellite mission, a CdZnTe detector prototype has been tested at the European Synchrotron Radiation Facility under an {approx}100% polarized gamma-ray beam. The spectroscopic, imaging, and timing performances were studied and in particular its potential as a polarimeter was evaluated. Polarization has been recognized as being a very important observational parameter in high energy astrophysics (>100 keV) and therefore this capability has been specifically included as part of the GRI mission proposal. The prototype detector tested was a 5 mm thick CdZnTe array with an 11x11 active pixel matrix (pixel area of 2.5x2.5 mm{sup 2}). The detector was irradiated by a monochromatic linearly polarized beam with a spot diameter of about 0.5 mm over the energy range between 150 and 750 keV. Polarimetric Q factors of 0.35 and double event relative detection efficiency of 20% were obtained. Further measurements were performed with a copper Laue monochromator crystal placed between the beam and the detector prototype. In this configuration we have demonstrated that a polarized beam does not change its polarization level and direction after undergoing a small angle (<1 deg.) Laue diffraction inside a crystal.

  17. Fiber fed x-ray/gamma ray imaging apparatus

    DOE Patents [OSTI]

    Hailey, C.J.; Ziock, K.P.

    1992-06-02T23:59:59.000Z

    X-ray/gamma ray imaging apparatus is disclosed for detecting the position, energy, and intensity of x-ray/gamma ray radiation comprising scintillation means disposed in the path of such radiation and capable of generating photons in response to such radiation; first photodetection means optically bonded to the scintillation means and capable of generating an electrical signal indicative of the intensity, and energy of the radiation detected by the scintillation means; second photodetection means capable of generating an electrical signal indicative of the position of the radiation in the radiation pattern; and means for optically coupling the scintillation means to the second photodetection means. The photodetection means are electrically connected to control and storage means which may also be used to screen out noise by rejecting a signal from one photodetection means not synchronized to a signal from the other photodetection means; and also to screen out signals from scattered radiation. 6 figs.

  18. Gamma-Ray Emission From Crushed Clouds in Supernova Remnants

    SciTech Connect (OSTI)

    Uchiyama, Yasunobu; Blandford, Roger D.; Funk, Stefan; /SLAC; Tajima, Hiroyasu; /Nagoya U., Solar-Terrestrial Environ. Lab.; Tanaka, Takaaki; /KIPAC, Menlo Park; ,

    2010-10-27T23:59:59.000Z

    It is shown that the radio and gamma-ray emission observed from newly-found 'GeV-bright' supernova remnants (SNRs) can be explained by a model, in which a shocked cloud and shock-accelerated cosmic rays (CRs) frozen in it are simultaneously compressed by the supernova blastwave as a result of formation of a radiative cloud shock. Simple reacceleration of pre-existing CRs is generally sufficient to power the observed gamma-ray emission through the decays of {pi}{sup 0}-mesons produced in hadronic interactions between high-energy protons (nuclei) and gas in the compressed-cloud layer. This model provides a natural account of the observed synchrotron radiation in SNRs W51C, W44 and IC 443 with flat radio spectral index, which can be ascribed to a combination of secondary and reaccelerated electrons and positrons.

  19. Gamma Ray Burst as Sources of Exotic Particles

    E-Print Network [OSTI]

    Morgan, Ian; De Pree, Erin; Tennyson, Kevin

    2015-01-01T23:59:59.000Z

    We consider the possible production of stable lightest first level KK particle (LKP) in baryonic gamma ray bursts (GRB) out flows. We numerically computed the energy-dependent cross-sections of Kaluza-Klein (KK) excitations for the Standard Model gauge bosons, photon and Z. Next, we determined the feasibility of producing these KK excitations in gamma-ray emitting regions of GRBs. We found that a GRB fireball that accelerates baryons to energies greater than 10^14 eV could produce KK excitations out to approximately 10^12 cm from the central engine, indicating that GRBs may be a significant source of the LKP. Finally, we explore the potential observational consequences of our results.

  20. THE BATSE 5B GAMMA-RAY BURST SPECTRAL CATALOG

    SciTech Connect (OSTI)

    Goldstein, Adam; Preece, Robert D.; Briggs, Michael S.; Burgess, J. Michael [University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Mallozzi, Robert S.; Fishman, Gerald J.; Kouveliotou, Chryssa [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Paciesas, William S. [Universities Space Research Association, 320 Sparkman Drive, Huntsville, AL 35805 (United States)

    2013-10-01T23:59:59.000Z

    We present systematic spectral analyses of gamma-ray bursts (GRBs) detected with the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma-Ray Observatory during its entire nine years of operation. This catalog contains two types of spectra extracted from 2145 GRBs, and fitted with five different spectral models resulting in a compendium of over 19,000 spectra. The models were selected based on their empirical importance to the spectral shape of many GRBs, and the analysis performed was devised to be as thorough and objective as possible. We describe in detail our procedures and criteria for the analyses, and present the bulk results in the form of parameter distributions. This catalog should be considered an official product from the BATSE Science Team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center (HEASARC)

  1. Color Superconductivity in Compact Stars and Gamma Ray Bursts

    E-Print Network [OSTI]

    A. Drago; A. Lavagno; G. Pagliara

    2003-04-08T23:59:59.000Z

    We study the effects of color superconductivity on the structure and formation of compact stars. We show that it is possible to satisfy most of recent observational boundaries on masses and radii if a diquark condensate forms in a hybrid or a quark star. Moreover, we find that a huge amount of energy, of the order of $10^{53}$ erg, can be released in the conversion from a (metastable) hadronic star into a (stable) hybrid or quark star, if the presence of a color superconducting phase is taken into account. Accordingly to the scenario proposed in Astrophys.J.586(2003)1250, the energy released in this conversion can power a Gamma Ray Burst. This mechanism can explain the recent observations indicating a delay, of the order of days or years, between a few Supernova explosions and the subsequent Gamma Ray Burst.

  2. Isotopic response with small scintillator based gamma-ray spectrometers

    DOE Patents [OSTI]

    Madden, Norman W. (Sparks, NV); Goulding, Frederick S. (Lafayette, CA); Asztalos, Stephen J. (Oakland, CA)

    2012-01-24T23:59:59.000Z

    The intrinsic background of a gamma ray spectrometer is significantly reduced by surrounding the scintillator with a second scintillator. This second (external) scintillator surrounds the first scintillator and has an opening of approximately the same diameter as the smaller central scintillator in the forward direction. The second scintillator is selected to have a higher atomic number, and thus has a larger probability for a Compton scattering interaction than within the inner region. Scattering events that are essentially simultaneous in coincidence to the first and second scintillators, from an electronics perspective, are precluded electronically from the data stream. Thus, only gamma-rays that are wholly contained in the smaller central scintillator are used for analytic purposes.

  3. Gamma-ray bursts, axion emission and string theory dilaton

    E-Print Network [OSTI]

    O. Bertolami

    1999-01-14T23:59:59.000Z

    The emission of axions from supernovae is an interesting possibility to account for the Gamma-Ray Bursts provided their energy can be effectively converted into electromagnetic energy elsewhere. The connection between supernova and gamma-ray bursts has been recently confirmed by the observed correlation between the burst of April 25, 1998 and the supernova SN1998bw. We argue that the axion convertion into photons can be more efficient if one considers the coupling between an intermediate scale axion and the string theory dilaton along with the inclusion of string loops. We also discuss the way dilaton dynamics may allow for a more effective energy exchange with electromagnetic radiation in the expansion process of fireballs.

  4. Power Density Spectra of Gamma-Ray Bursts

    E-Print Network [OSTI]

    Andrei M. Beloborodov

    1999-11-08T23:59:59.000Z

    Power density spectra (PDSs) of long gamma-ray bursts provide useful information on GRBs, indicating their self-similar temporal structure. The best power-law PDSs are displayed by the longest bursts (T_90 > 100 s) in which the range of self-similar time scales covers more than 2 decades. Shorter bursts have apparent PDS slopes more strongly affected by statistical fluctuations. The underlying power law can then be reproduced with high accuracy by averaging the PDSs for a large sample of bursts. This power-law has a slope alpha\\approx -5/3 and a sharp break at 1 Hz. The power-law PDS provides a new sensitive tool for studies of gamma-ray bursts. In particular, we calculate the PDSs of bright bursts in separate energy channels. The PDS flattens in the hard channel (h\

  5. Gravitational collapse as the source of gamma-ray bursts

    E-Print Network [OSTI]

    V. V. Sokolov

    2008-05-21T23:59:59.000Z

    If the threshold for $e^{-}e^{+}$ pair production depends on an angle between photon momenta, and if the $\\gamma$-rays are collimated right in gamma-ray burst (GRB) source then another solution of the compactness problem is possible. The list of basic assumptions of the scenario describing the GRB with energy release $< 10^{49}$ erg is adduced: the matter is about an alternative to the ultrarelativistic fireball if all long-duration GRBs are physically connected with core-collapse supernovae (SNe). The questions about radiation pressure and how the jet arises on account of even a small radiation field asymmetry in a compact GRB source of size $\\lesssim 10^8$ cm, and observational consequences of the compact model of GRBs are considered.

  6. High energy gamma-rays from massive binary systems

    E-Print Network [OSTI]

    W. Bednarek

    2008-06-27T23:59:59.000Z

    During last years a few massive binary systems have been detected in the TeV gamma-rays. This gamma-ray emission is clearly modulated with the orbital periods of these binaries suggesting its origin inside the binary system. In this paper we summarize the anisotropic IC e-p pair cascade model as likely explanation of these observations. We consider scenarios in which particles are accelerated to relativistic energies, either due to the presence of an energetic pulsar inside the binary, or as a result of accretion process onto the compact object during which the jet is launched from the inner part of the accretion disk, or in collisions of stellar winds from the massive companions.

  7. Radiation detection system for portable gamma-ray spectroscopy

    DOE Patents [OSTI]

    Rowland, Mark S. (Alamo, CA); Howard, Douglas E. (Livermore, CA); Wong, James L. (Dublin, CA); Jessup, James L. (Tracy, CA); Bianchini, Greg M. (Livermore, CA); Miller, Wayne O. (Livermore, CA)

    2006-06-20T23:59:59.000Z

    A portable gamma ray detection apparatus having a gamma ray detector encapsulated by a compact isolation structure having at least two volumetrically-nested enclosures where at least one is a thermal shield. The enclosures are suspension-mounted to each other to successively encapsulate the detector without structural penetrations through the thermal shields. A low power cooler is also provided capable of cooling the detector to cryogenic temperatures without consuming cryogens, due to the heat load reduction by the isolation structure and the reduction in the power requirements of the cooler. The apparatus also includes a lightweight portable power source for supplying power to the apparatus, including to the cooler and the processing means, and reducing the weight of the apparatus to enable handheld operation or toting on a user's person.

  8. Acceleration at Relativistic Shocks in Gamma-Ray Bursts

    E-Print Network [OSTI]

    Baring, M G

    1999-01-01T23:59:59.000Z

    Most recent extragalactic models of gamma-ray bursts consider the expansion of a relativistic blast wave, emanating from a solar-mass type progenitor, into the surrounding interstellar medium as the site for their activity. The popular perception is that the optical afterglows result from the external shock interface, while the prompt transient gamma-ray signal arises from multiple shocks internal to the expansion. This paper illustrates a number of acceleration properties of relativistic and ultrarelativistic shocks that pertain to GRB models, by way of a standard Monte Carlo simulation. Computations of the spectral shape, the range of spectral indices, and the energy gain per shock crossing are presented, as functions of the shock speed and the type of particle scattering.

  9. Neutron and Gamma Ray Pulse Shape Discrimination with Polyvinyltoluene

    SciTech Connect (OSTI)

    Lintereur, Azaree T.; Ely, James H.; Stave, Jean A.; McDonald, Benjamin S.

    2012-03-01T23:59:59.000Z

    The goal of this was research effort was to test the ability of two poly vinyltoluene research samples to produce recordable, distinguishable signals in response to gamma rays and neutrons. Pulse shape discrimination was performed to identify if the signal was generated by a gamma ray or a neutron. A standard figure of merit for pulse shape discrimination was used to quantify the gamma-neutron pulse separation. Measurements were made with gamma and neutron sources with and without shielding. The best figure of merit obtained was 1.77; this figure of merit was achieved with the first sample in response to an un-moderated 252Cf source shielded with 5.08 cm of lead.

  10. Planetary Produced Axionlike Particles and Gamma-Ray Flashes

    SciTech Connect (OSTI)

    Liolios, Anastasios [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2008-12-24T23:59:59.000Z

    Axion-like particles could be created in nuclear disintegrations and deexitations of natural radionuclides present in the interior of the planets. For the Earth and the other planets with a surrounding magnetosphere, axion production could result to gamma and X-ray emission, originating from axion to photon conversion in the planetary magnetic fields. The estimated planetary axion fluxes as well as the related gamma ray fluxes from Earth and the giant planets of our solar system are given along with the axion coupling to ordinary matter. A possible connection with the enigmatic Terrestrial Gamma-ray Flashes (TGFs) discovered in 1994 by CGRO/BATSE and also detected with the RHESSI satellite, is also discussed.

  11. Radio and gamma-ray connection in relativistic jets

    E-Print Network [OSTI]

    Orienti, M

    2015-01-01T23:59:59.000Z

    Relativistic jets are one of the most powerful manifestations of the release of energy related to the supermassive black holes at the centre of active galactic nuclei (AGN). Their emission is observed across the entire electromagnetic spectrum, from the radio band to gamma rays. Despite decades of efforts, many aspects of the physics of relativistic jets remain elusive. In particular, the location and the mechanisms responsible for the high-energy emission and the connection of the variability at different wavelengths are among the greatest challenges in the study of AGN. Recent high resolution radio observations of flaring objects locate the high-energy emitting region downstream the jet at parsec scale distance from the central engine, posing questions on the nature of the seed photons upscattered to gamma-rays. Furthermore, monitoring campaigns of the most active blazars indicate that not all the high energy flares have the same characteristics in the various energy bands, even from the same source, making...

  12. Possible Effects of Pair Echoes on Gamma-Ray Burst Afterglow Emission

    E-Print Network [OSTI]

    Kohta Murase; Bing Zhang; Keitaro Takahashi; Shigehiro Nagataki

    2009-02-27T23:59:59.000Z

    High-energy emission from gamma-ray bursts (GRBs) is widely expected but had been sparsely observed until recently when the Fermi satellite was launched. If >TeV gamma rays are produced in GRBs and can escape from the emission region, they are attenuated by the cosmic infrared background photons, leading to regeneration of GeV-TeV secondary photons via inverse-Compton scattering. This secondary emission can last for a longer time than the duration of GRBs, and it is called a pair echo. We investigate how this pair echo emission affects spectra and light curves of high energy afterglows, considering not only prompt emission but also afterglow as the primary emission. Detection of pair echoes is possible as long as the intergalactic magnetic field (IGMF) in voids is weak. We find (1) that the pair echo from the primary afterglow emission can affect the observed high-energy emission in the afterglow phase after the jet break, and (2) that the pair echo from the primary prompt emission can also be relevant, but only when significant energy is emitted in the TeV range, typically E_{gamma, >0.1 TeV} > (Y/(1+Y)) epsilon_e E_k. Even non-detections of the pair echoes could place interesting constraints on the strength of IGMF. The more favorable targets to detect pair echoes may be the "naked" GRBs without conventional afterglow emission, although energetic naked GRBs would be rare. If the IGMF is weak enough, it is predicted that the GeV emission extends to >30-300 s.

  13. Dark gamma-ray bursts: possible role of multiphoton processes

    E-Print Network [OSTI]

    Mark E. Perel'man

    2009-07-27T23:59:59.000Z

    The absence of optical afterglow at some gamma-ray bursts (so called dark bursts) requires analyses of physical features of this phenomenon. It is shown that such singularity can be connected with multiphoton processes of frequencies summation in the Rayleigh- Jeans part of spectra, their pumping into higher frequencies. It can be registered most probably on young objects with still thin plasma coating, without further thermalization, i.e. soon after a prompt beginning of the explosive activity.

  14. Gamma-Ray Burst Detection with INTEGRAL/SPI

    E-Print Network [OSTI]

    Andreas von Kienlin; Nikolas Arend; Giselher Lichti; Andrew Strong; Paul Connell

    2004-07-05T23:59:59.000Z

    The spectrometer SPI, one of the two main instruments of the INTEGRAL spacecraft, has strong capabilities in the field of Gamma-Ray Burst (GRB) detections. In its 16 deg field of view (FoV) SPI is able to trigger and to localize GRBs with an accuracy for strong bursts better than 1 deg. The expected GRB detection rate is about one per month.

  15. THE ENGINES BEHIND SUPERNOVAE AND GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    FRYER, CHRISTOPHER LEE [Los Alamos National Laboratory

    2007-01-23T23:59:59.000Z

    The authors review the different engines behind supernova (SNe) and gamma-ray bursts (GRBs), focusing on those engines driving explosions in massive stars: core-collapse SNe and long-duration GRBs. Convection and rotation play important roles in the engines of both these explosions. They outline the basic physics and discuss the wide variety of ways scientists have proposed that this physics can affect the supernova explosion mechanism, concluding with a review of the current status in these fields.

  16. On the origin of Gamma Ray Burst radiation

    E-Print Network [OSTI]

    G. Ghisellini

    2001-01-17T23:59:59.000Z

    In the standard internal shock model, the observed X and gamma-ray radiation is assumed to be produced by synchrotron emission. I will show that there are serious problems with this interpretation, calling for other radiation mechanisms, such as quasi-thermal Comptonization and/or Compton drag processes, or both. These new ideas can have important consequences on the more general internal shock scenario, and can be tested by future observations.

  17. Crystal diffraction lens telescope for focusing nuclear gamma rays

    SciTech Connect (OSTI)

    Smither, R.K.; Fernandez, P.B.; Graber, T. [Argonne National Lab., IL (United States). Advanced Photon Source; Ballmoos, P. von; Naya, J.; Albernhe, F.; Vedrenne, G. [Centre d`Etude Spatiale des Rayonnements, Toulouse (France); Faiz, M. [KFUPM, Dhahran (Saudi Arabia). Physics Dept.

    1996-08-01T23:59:59.000Z

    A crystal diffraction lens was constructed at Argonne National Laboratory for use as a telescope to focus nuclear gamma rays. It consisted of 600 single crystals of germanium arranged in 8 concentric rings. The mounted angle of each crystal was adjusted to intercept and diffract the incoming gamma rays with an accuracy of a few arc sec. The performance of the lens was tested in two ways. In one case, the gamma rays were focused on a single medium size germanium detector. In the second case, the gamma rays were focused on the central germanium detector of a 3 x 3 matrix of small germanium detectors. The efficiency, image concentration and image quality, and shape were measured. The tests performed with the 3 x 3 matrix detector system were particularly interesting. The wanted radiation was concentrated in the central detector. The 8 other detectors were used to detect the Compton scattered radiation, and their energy was summed with coincident events in the central detector. This resulted in a detector with the efficiency of a large detector (all 9 elements) and the background of a small detector (only the central element). The use of the 3 x 3 detector matrix makes it possible to tell if the source is off axis and, if so, to tell in which direction. The crystal lens acts very much like a simple convex lens for visible light. Thus if the source is off to the left then the image will focus off to the right illuminating the detector on the right side: telling one in which direction to point the telescope. Possible applications of this type of crystal lens to balloon and satellite experiments will be discussed.

  18. Capture Gamma-Ray Libraries for Nuclear Applications

    SciTech Connect (OSTI)

    Sleaford, B.W.; Firestone, Richard B.; Summers, N.; Escher, J.; Hurst, A.; Krticka, M.; Basunia, S.; Molnar, G.; Belgya, T.; Revay, Z.; Choi, H.D.

    2010-05-01T23:59:59.000Z

    The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. This can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research Project. EGAF has been used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90percent of all the decay energy an is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. We use CASINO, a version of DICEBOX that is modified for this purpose. This can be used to simulate the neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modelling of unknown assemblies.

  19. Short Gamma-Ray Bursts from Binary Neutron Star Mergers

    E-Print Network [OSTI]

    Roland Oechslin; Thomas Janka

    2006-04-27T23:59:59.000Z

    We present the results from new relativistic hydrodynamic simulations of binary neutron star mergers using realistic non-zero temperature equations of state. We vary several unknown parameters in the system such as the neutron star (NS) masses, their spins and the nuclear equation of state. The results are then investigated with special focus on the post-merger torus-remnant system. Observational implications on the Gamma-ray burst (GRB) energetics are discussed and compared with recent observations.

  20. The Supernovae Associated with Gamma-Ray Bursts

    E-Print Network [OSTI]

    Thomas Matheson

    2004-10-27T23:59:59.000Z

    Supernovae (SNe) were long suspected as possible progenitors of gamma-ray bursts (GRBs). The arguments relied on circumstantial evidence. Several recent GRBs, notably GRB 030329, have provided direct, spectroscopic evidence that SNe and GRBs are related. The SNe associated with GRBs are all of Type Ic, implying a compact progenitor, which has implications for GRB models. Other peculiar Type Ic SNe may help to expand understanding of the mechanisms involved.

  1. The HAWC Gamma-Ray Observatory: Observations of Cosmic Rays

    E-Print Network [OSTI]

    Abeysekara, A U; Alvarez, C; Álvarez, J D; Arceo, R; Arteaga-Velázquez, J C; Solares, H A Ayala; Barber, A S; Baughman, B M; Bautista-Elivar, N; Belmont, E; BenZvi, S Y; Berley, D; Rosales, M Bonilla; Braun, J; Caballero-Lopez, R A; Caballero-Mora, K S; Carramińana, A; Castillo, M; Cotti, U; Cotzomi, J; de la Fuente, E; De León, C; DeYoung, T; Hernandez, R Diaz; Díaz-Vélez, J C; Dingus, B L; DuVernois, M A; Ellsworth, R W; Fernandez, A; Fiorino, D W; Fraija, N; Galindo, A; Garfias, F; González, L X; González, M M; Goodman, J A; Grabski, V; Gussert, M; Hampel-Arias, Z; Hui, C M; Hüntemeyer, P; Imran, A; Iriarte, A; Karn, P; Kieda, D; Kunde, G J; Lara, A; Lauer, R J; Lee, W H; Lennarz, D; Vargas, H León; Linares, E C; Linnemann, J T; Longo, M; Luna-GarcIa, R; Marinelli, A; Martinez, H; Martinez, O; Martínez-Castro, J; Matthews, J A J; Miranda-Romagnoli, P; Moreno, E; Mostafá, M; Nava, J; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T; Patricelli, B; Pelayo, R; Pérez-Pérez, E G; Pretz, J; Rivičre, C; Rosa-González, D; Salazar, H; Salesa, F; Sanchez, F E; Sandoval, A; Santos, E; Schneider, M; Silich, S; Sinnis, G; Smith, A J; Sparks, K; Springer, R W; Taboada, I; Toale, P A; Tollefson, K; Torres, I; Ukwatta, T N; Villaseńor, L; Weisgarber, T; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Younk, P W; Zaborov, D; Zepeda, A; Zhou, H

    2013-01-01T23:59:59.000Z

    We describe measurements of GeV and TeV cosmic rays with the High-Altitude Water Cherenkov Gamma-Ray Observatory, or HAWC. The measurements include the observation of the shadow of the moon; the observation of small-scale and large-scale angular clustering of the TeV cosmic rays; the prospects for measurement of transient solar events with HAWC; and the observation of Forbush decreases with the HAWC engineering array and HAWC-30.

  2. Search for neutrinos from Gamma-Ray Bursts with ANTARES

    E-Print Network [OSTI]

    Eleonora Presani

    2011-04-20T23:59:59.000Z

    A method to search for neutrino induced showers from gamma-ray bursts in the ANTARES detector is presented. ANTARES consists of a three-dimensional array of photosensitive devices that measure Cherenkov light induced by charged particles produced by high energy neutrinos interacting in the detector vicinity. The shower channel is complementary to the more commonly used upgoing muon channel. The corresponding detection volume is smaller, but has the advantage of being sensitive to neutrinos of any flavour.

  3. NEUTRON AND GAMMA RAY DETECTION FOR BORDER SECURITY APPLICATIONS

    SciTech Connect (OSTI)

    Kouzes, Richard T.

    2010-05-21T23:59:59.000Z

    Countries around the world are deploying radiation detection instrumentation to interdict the illegal shipment of radioactive material crossing international borders. These efforts include deployments in the U.S. and in a number of other countries by governments and international organizations. Most deployed radiation portal monitor systems are based on plastic scintillator for gamma-ray detection and 3He tubes for neutron detection. The approach to this homeland security application, and lessons learned, are discussed.

  4. Hints of the Existence of Axion-Like-Particles From the Gamma-Ray Spectra of Cosmological Sources

    SciTech Connect (OSTI)

    Sanchez-Conde, M.A.; /IAA, Granada /SLAC; Paneque, D.; Bloom, E.; /KIPAC, Menlo Park; Prada, F.; /IAA, Granada /UC, Santa Cruz; Dominguez, A.; /IAA, Granada /Seville U.; ,

    2009-06-23T23:59:59.000Z

    Axion Like Particles (ALPs) are predicted to couple with photons in the presence of magnetic fields. This effect may lead to a significant change in the observed spectra of gamma-ray sources such as AGNs. Here we carry out a detailed study that for the first time simultaneously considers in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. An efficient photon/axion mixing in the source always means an attenuation in the photon flux, whereas the mixing in the intergalactic medium may result in a decrement and/or enhancement of the photon flux, depending on the distance of the source and the energy considered. Interestingly, we find that decreasing the value of the intergalactic magnetic field strength, which decreases the probability for photon/axion mixing, could result in an increase of the expected photon flux at Earth if the source is far enough. We also find a 30% attenuation in the intensity spectrum of distant sources, which occurs at an energy that only depends on the properties of the ALPs and the intensity of the intergalactic magnetic field, and thus independent of the AGN source being observed. Moreover, we show that this mechanism can easily explain recent puzzles in the spectra of distant gamma-ray sources, like the possible detection of TeV photons from 3C 66A (a source located at z=0.444) by MAGIC and VERITAS, which should not happen according to conventional models of photon propagation over cosmological distances. Another puzzle is the recent published lower limit to the EBL intensity at 3.6 {micro}m (which is almost twice larger as the previous one), which implies very hard spectra for some detected TeV gamma-ray sources located at z=0.1-0.2. The consequences that come from this work are testable with the current generation of gamma-ray instruments, namely Fermi (formerly known as GLAST) and imaging atmospheric Cherenkov telescopes like CANGAROO, HESS, MAGIC and VERITAS.

  5. TWO POPULATIONS OF GAMMA-RAY BURST RADIO AFTERGLOWS

    SciTech Connect (OSTI)

    Hancock, P. J.; Gaensler, B. M.; Murphy, T., E-mail: Paul.Hancock@Sydney.edu.au [Also at Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), The University of Sydney, Sydney, NSW 2006, Australia. (Australia)

    2013-10-20T23:59:59.000Z

    The detection rate of gamma-ray burst (GRB) afterglows is ?30% at radio wavelengths, much lower than in the X-ray (?95%) or optical (?70%) bands. The cause of this low radio detection rate has previously been attributed to limited observing sensitivity. We use visibility stacking to test this idea, and conclude that the low detection rate is instead due to two intrinsically different populations of GRBs: radio-bright and radio-faint. We calculate that no more than 70% of GRB afterglows are truly radio-bright, leaving a significant population of GRBs that lack a radio afterglow. These radio-bright GRBs have higher gamma-ray fluence, isotropic energies, X-ray fluxes, and optical fluxes than the radio-faint GRBs, thus confirming the existence of two physically distinct populations. We suggest that the gamma-ray efficiency of the prompt emission is responsible for the difference between the two populations. We also discuss the implications for future radio and optical surveys.

  6. Are we observing Lorentz violation in gamma ray bursts?

    E-Print Network [OSTI]

    Theodore G. Pavlopoulos

    2005-08-12T23:59:59.000Z

    From recent observations of gamma-ray bursts (GRBs), it appears that spectral time lags between higher-energy gamma rays photons and lower-energy photons vary with energy difference and time (distance) traveled. These lags appear to be smaller for the most luminous (close) bursts but larger for the fainter (farther away) bursts. From this observation, it has been suggested that it might be possible to determine the distance (L) these bursts have traveled from these time lags alone, without performing any red-shift measurements. These observed spreads (dispersion) of high-energy electromagnetic pulses of different energies with time contradict the special theory of relativity (STR). However, extended theories (ET) of the STR have been developed that contain a dispersive term, predicting the above observations. An example of such an ET is presented, allowing us to derive a relationship between time lags of gamma rays of different energies and distance L traveled from their origin. In addition, this theory predicts the origin of X-ray flashes.

  7. Gamma-ray lines from SN2014J

    E-Print Network [OSTI]

    Siegert, Thomas

    2015-01-01T23:59:59.000Z

    On 21 January 2014, SN2014J was discovered in M82 and found to be the closest type Ia supernova (SN Ia) in the last four decades. INTEGRAL observed SN2014J from the end of January until late June for a total exposure time of about 7 Ms. SNe Ia light curves are understood to be powered by the radioactive decay of iron peak elements of which $^{56}$Ni is dominantly synthesized during the thermonuclear disruption of a CO white dwarf (WD). The measurement of $\\gamma$-ray lines from the decay chain $^{56}$Ni$\\rightarrow$$^{56}$Co$\\rightarrow$$^{56}$Fe provides unique information about the explosion in supernovae. Canonical models assume $^{56}$Ni buried deeply in the supernova cloud, absorbing most of the early $\\gamma$-rays, and only the consecutive decay of $^{56}$Co should become directly observable through the overlaying material several weeks after the explosion when the supernova envelope dilutes as it expands. Surprisingly, with the spectrometer on INTEGRAL, SPI, we detected $^{56}$Ni $\\gamma$-ray lines at ...

  8. The Gamma Ray Burst Rate at High Photon Energies

    E-Print Network [OSTI]

    Karl Mannheim; Dieter Hartmann; Burkhardt Funk

    1996-05-17T23:59:59.000Z

    Some gamma-ray burst (GRB) spectra exhibit high energy tails with the highest photon energy detected at 18 GeV. The spectral slope of the high-energy tails is sufficiently flat in nu F_nu to consider the possibility of their detection at still higher energies. We calculate how many bursts can reasonably be expected above a given energy threshold for a cosmological distribution of bursts satisfying the observed apparent brightness distribution. The crucial point is that the gamma-ray absorption by pair production in the intergalactic diffuse radiation field eliminates bursts from beyond the gamma-ray horizon tau ~ 1, thus drastically reducing the number of bursts at high energies. Our results are consistent with the non-detection of bursts by current experiments in the 100 GeV to 100 TeV energy range. For the earth-bound detector array MILAGRO, we predict a maximal GRB rate of ~ 10 events per year. The Whipple Observatory can detect, under favorable conditions, ~1 event per year. The event rate for the HEGRA array is ~ 0.01 per year. Detection of significantly higher rates of bursts would severely challenge cosmological burst scenarios.

  9. Gamma-Ray Bursts Above 1 GeV

    E-Print Network [OSTI]

    Matthew G. Baring

    1997-11-21T23:59:59.000Z

    One of the principal results obtained by the Compton Gamma Ray Observatory relating to the study of gamma-ray bursts was the detection by the EGRET instrument of energetic ($>$100 MeV) photons from a handful of bright bursts. The most extreme of these was the single 18 GeV photon from the GRB940217 source. Given EGRET's sensitivity and limited field of view, the detection rate implies that such high energy emission may be ubiquitous in bursts. Hence expectations that bursts emit out to at least TeV energies are quite realistic, and the associated target-of-opportunity activity of the TeV gamma-ray community is well-founded. This review summarizes the observations and a handful of theoretical models for generating GeV--TeV emission in bursts sources, outlining possible ways that future positive detections could discriminate between different scenarios. The power of observations in the GeV--TeV range to distinguish between spectral structure intrinsic to bursts and that due to the intervening medium between source and observer is also discussed.

  10. Thermal-neutron capture gamma-rays. Volume 1

    SciTech Connect (OSTI)

    Tuli, J.K. [National Nuclear Data Center, Upton, NY (United States)

    1997-05-01T23:59:59.000Z

    The energy and photon intensity of gamma rays as seen in thermal-neutron capture are presented in ascending order of gamma energy. All those gamma-rays with intensity of {ge} 2% of the strongest transition are included. The two strongest transitions seen for the target nuclide are indicated in each case. Where the target nuclide mass number is indicated as nat the natural target was used. The gamma energies given are in keV. The gamma intensities given are relative to 100 for the strongest transition. All data for A > 44 are taken from Evaluated Nuclear Structure Data File (4/97), a computer file of evaluated nuclear structure data maintained by the National Nuclear Data Center, Brookhaven National Laboratory, on behalf of the Nuclear Structure and Decay and Decay Data network, coordinated by the International Atomic Energy Agency, Vienna. These data are published in Nuclear Data Sheets, Academic Press, San Diego, CA. The data for A {le} 44 is taken from ``Prompt Gamma Rays from Thermal-Neutron Capture,`` M.A. Lone, R.A. Leavitt, D.A. Harrison, Atomic Data and Nuclear Data Tables 26, 511 (1981).

  11. ON THE RECENTLY DISCOVERED CORRELATIONS BETWEEN GAMMA-RAY AND X-RAY PROPERTIES OF GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Dado, Shlomo; Dar, Arnon [Physics Department, Technion, Haifa 32000 (Israel)

    2013-09-20T23:59:59.000Z

    Recently, many correlations between the prompt {gamma}-ray emission properties and the X-ray afterglow properties of gamma-ray bursts (GRBs) have been inferred from a comprehensive analysis of the X-ray light curves of more than 650 GRBs measured with the Swift X-Ray Telescope (Swift/XRT) during the years 2004-2010. We show that these correlations are predicted by the cannonball (CB) model of GRBs. They result from the dependence of GRB observables on the bulk motion Lorentz factor and viewing angle of the jet of highly relativistic plasmoids (CBs) that produces the observed radiations by interaction with the medium through which it propagates. Moreover, despite their different physical origins, long GRBs (LGRBs) and short-hard bursts (SHBs) in the CB model share similar kinematic correlations, which can be combined into triple correlations satisfied by both LGRBs and SHBs.

  12. A study of the performance parameters of the High Altitude Gamma Ray (HAGAR) telescope system at Ladakh in India

    E-Print Network [OSTI]

    Shyamasundar, R.K.

    results of Monte Carlo simulations for the High Altitude Gamma Ray (HAGAR) telescope array which detects High Altitude GAmma Ray (HAGAR) telescope system is designed to detect very high energy gamma rays fromA study of the performance parameters of the High Altitude Gamma Ray (HAGAR) telescope system

  13. HIGH PURITY GE GAMMA-RAY SPECTROMETER ON JAPANESE LUNAR POLAR ORBITER , M.-N. Kobayashi1

    E-Print Network [OSTI]

    Berezhnoi, Aleksei A.

    of three parts; gamma-ray detector (GRD), compressor driver unit (CDU) and gamma- ray and particle purified Ge detector is employed as a main detector, by which gamma-rays can be detected in the energyHIGH PURITY GE GAMMA-RAY SPECTROMETER ON JAPANESE LUNAR POLAR ORBITER SELENE. N. Hasebe1 , M

  14. GRB 050117: SIMULTANEOUS GAMMA-RAY AND X-RAY OBSERVATIONS WITH THE SWIFT SATELLITE Joanne E. Hill,1, 2

    E-Print Network [OSTI]

    Zhang, Bing

    The Swift Gamma-Ray Burst Explorer performed its first autonomous, X-ray follow-up to a newly detected GRB from the XRT position. Subject headingg: gamma rays: bursts 1. INTRODUCTION The Swift Gamma-ray Burst Explorer (Gehrels et al. 2004) was launched on 2004 November 20 to study gamma-ray bursts (GRBs) over

  15. THE HIGH-ENERGY GAMMA-RAY FLUENCE AND ENERGY SPECTRUM OF GRB 970417a FROM OBSERVATIONS WITH MILAGRITO

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    of this observation are discussed. Subject headings: gamma rays: bursts -- gamma rays: observations 1. INTRODUCTION Some of the most important contributions to our under- standing of gamma-ray bursts (GRBs) have comeTHE HIGH-ENERGY GAMMA-RAY FLUENCE AND ENERGY SPECTRUM OF GRB 970417a FROM OBSERVATIONS

  16. Gravitational collapse of a spherical star with heat flow as a possible energy mechanism of gamma-ray bursts

    E-Print Network [OSTI]

    Zhe Chang; Cheng-Bo Guan; Chao-Guang Huang; Xin Li

    2008-03-26T23:59:59.000Z

    We investigate the gravitational collapse of a spherically symmetric, inhomogeneous star, which is described by a perfect fluid with heat flow and satisfies the equation of state $p=\\rho/3$ at its center. In the process of the gravitational collapsing, the energy of the whole star is emitted into space. And the remaining spacetime is a Minkowski one without a remnant at the end of the process. For a star with a solar mass and solar radius, the total energy emitted is at the order of $10^{54}$ {\\rm erg}, and the time-scale of the process is about $8s$. These are in the typical values for a gamma-ray burst. Thus, we suggest the gravitational collapse of a spherical star with heat flow as a possible energy mechanism of gamma-ray bursts.

  17. An Algorithm for Detecting Quantum-Gravity Photon Dispersion in Gamma-Ray Bursts: DISCAN

    E-Print Network [OSTI]

    Jeffrey D. Scargle; Jay P. Norris; Jerry T. Bonnell

    2007-09-01T23:59:59.000Z

    DisCan is a new algorithm implementing photon dispersion cancellation in order to measure energy-dependent delays in variable sources. This method finds the amount of reversed dispersion that optimally cancels any actual dispersion present. It applies to any time- and energy-tagged photon data, and can avoid binning in both time and energy. The primary motivation here is the search for quantum gravity based dispersion in future gamma ray burst data from the Gamma Ray Large Area Space Telescope (GLAST). Extrapolation of what is know about bursts at lower energies yields a reasonable prospect that photon dispersion effects consistent with some quantum gravity formalisms may be detected in sufficiently bright bursts. Short bursts have no or very small inherent lags, and are therefore better prospects than long ones, but even they suffer systematic error due to pulse asymmetry that may yield an irreducible uncertainty. We note that data at energies higher than about 0.1 TeV may not be useful for detecting dispersion in GRBs. Of several variants of the proposed algorithm, one based on Shannon information is consistently somewhat superior to all of the others we investigated.

  18. Elemental mapping of the moon using gamma rays : past, present, and future /

    SciTech Connect (OSTI)

    Reedy, R. C. (Robert C.)

    2001-01-01T23:59:59.000Z

    The energies and intensities of gamma rays From a planetary surface can be used to infer the elemental composition of an object with no or a thin atmosphere. The Apollo gamma-ray spectrometers in 1972 and 1973 produced many of the results for the distribution of elements in the Moon that are now generally well accepted. Lunar Prospector in 1998 and 1999 globally mapped the Moon with gamma rays and neutrons. Both missions used spectrometers with poor energy resolution ({approx}8-10%). The Japanese plan to send a high-resolution germanium gamma-ray spectrometer to the Moon in about 2004 on their SELENE mission. However, little has been done since the 1970s on the models used to unfold planetary gamma-ray spectra. More work needs to be done on understanding what to expect in future gamma-ray spectra and how to unfold such data.

  19. UNIVERSITY OF CALIFORNIA, SANTA CRUZ SANTA CRUZ INSTITUTE FOR PARTICLE PHYSICS

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    . The Fermi Gamma-ray Burst Monitor (GBM) provides spectral and timing information of gamma-ray bursts in High-Energy Gamma-Ray Astrophysics with the Fermi Gamma-ray Space Telescope The Santa Cruz Institute for Particle Physics (SCIPP) invites applications for a Postdoctoral Scholar in the field of high-energy gamma-ray

  20. Are Durations of Weak Gamma-Ray Bursts Reliable?

    E-Print Network [OSTI]

    Maarten Schmidt

    2005-08-16T23:59:59.000Z

    Simulations in the GUSBAD Catalog of gamma-ray bursts suggest that the apparent duration of a burst decreases as its amplitude is decreased. We see no evidence for this effect in the BATSE catalog. We show that for a burst at the detection limit, the typical signal-to-noise ratio at the edges of the T90 duration is around 1.5, suggesting that T90 must be quite uncertain. The situation for T50 is less unfavorable. Simulations using the exact procedure to derive the durations in the BATSE catalog would be useful in quantifying the effect.

  1. INTERPLANETARY NETWORK LOCALIZATIONS OF KONUS SHORT GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Pal'shin, V. D.; Svinkin, D. S.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Mazets, E. P.; Oleynik, P. P.; Ulanov, M. V. [Ioffe Physical Technical Institute, St. Petersburg, 194021 (Russian Federation); Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Cline, T.; Trombka, J.; McClanahan, T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mitrofanov, I. G.; Golovin, D. V.; Kozyrev, A. S.; Litvak, M. L.; Sanin, A. B. [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); Boynton, W.; Fellows, C.; Harshman, K., E-mail: val@mail.ioffe.ru [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); and others

    2013-08-15T23:59:59.000Z

    Between the launch of the Global Geospace Science Wind spacecraft in 1994 November and the end of 2010, the Konus-Wind experiment detected 296 short-duration gamma-ray bursts (including 23 bursts which can be classified as short bursts with extended emission). During this period, the Interplanetary Network (IPN) consisted of up to 11 spacecraft, and using triangulation, the localizations of 271 bursts were obtained. We present the most comprehensive IPN localization data on these events. The short burst detection rate, {approx}18 yr{sup -1}, exceeds that of many individual experiments.

  2. Can Sequentially Linked Gamma-Ray Bursts Nullify Randomness?

    E-Print Network [OSTI]

    Charles Fleischer

    2012-05-02T23:59:59.000Z

    In order to nullify the property of randomness perceived in the dispersion of gamma-ray bursts (GRB's) we introduce two new procedures. 1. Create a segmented group of sequentially linked GRB's and quantify the resultant angles. 2. Create segmented groups of sequentially linked GRB's in order to identify the location of GRB's that are positioned at equidistance, by using the selected GRB as the origin for a paired point circle, where the circumference of said circle intercepts the location of other GRB's in the same group.

  3. Gamma ray burst distances and the timescape cosmology

    E-Print Network [OSTI]

    Peter R. Smale

    2011-08-22T23:59:59.000Z

    Gamma ray bursts can potentially be used as distance indicators, providing the possibility of extending the Hubble diagram to redshifts ~7. Here we follow the analysis of Schaefer (2007), with the aim of distinguishing the timescape cosmological model from the \\LambdaCDM model by means of the additional leverage provided by GRBs in the range 2 < z < 7. We find that the timescape model fits the GRB sample slightly better than the \\LambdaCDM model, but that the systematic uncertainties are still too little understood to distinguish the models.

  4. Gravitational radiation from long gamma-ray bursts

    E-Print Network [OSTI]

    Maurice H. P. M. van Putten

    2001-02-11T23:59:59.000Z

    Long gamma-ray bursts (GRBs) are probably powered by high-angular momentum black hole-torus systems in suspended accretion. The torus will radiate gravitational waves as non-axisymmetric instabilities develop. The luminosity in gravitational-wave emissions is expected to compare favorably with the observed isotropic equivalent luminosity in GRB-afterglow emissions. This predicts that long GRBs are potentially the most powerful LIGO/VIRGO burst-sources in the Universe. Their frequency-dynamics is characterized by a horizontal branch in the $\\dot{f}(f)-$diagram.

  5. High Energy Neutrinos from Cosmological Gamma-Ray Burst Fireballs

    E-Print Network [OSTI]

    Eli Waxman; John Bahcall

    1997-01-30T23:59:59.000Z

    Observations suggest that $\\gamma$-ray bursts (GRBs) are produced by the dissipation of the kinetic energy of a relativistic fireball. We show that a large fraction, $\\ge 10%$, of the fireball energy is expected to be converted by photo-meson production to a burst of $\\sim10^{14} eV$ neutrinos. A km^2 neutrino detector would observe at least several tens of events per year correlated with GRBs, and test for neutrino properties (e.g. flavor oscillations, for which upward moving $\\tau$'s would be a unique signature, and coupling to gravity) with an accuracy many orders of magnitude better than is currently possible.

  6. Reverse Shock Emission in Gamma-ray Bursts Revisited

    E-Print Network [OSTI]

    Gao, He

    2015-01-01T23:59:59.000Z

    A generic synchrotron external shock model is the widely preferred paradigm used to interpret the broad-band afterglow data of gamma-ray bursts (GRBs), including predicted observable signatures from a reverse shock which have been confirmed by observations. Investigations of the nature of the reverse shock emission can provide valuable insights into the intrinsic properties of the GRB ejecta. Here we briefly review the standard and the extended models of the reverse shock emission, discussing the connection between the theory and observations, including the implications of the latest observational advances.

  7. Long gamma-ray bursts trace the star formation history

    SciTech Connect (OSTI)

    Dado, Shlomo; Dar, Arnon [Physics Department, Technion, Haifa 32000 (Israel)

    2014-04-10T23:59:59.000Z

    We show that if the broad-line supernova explosions of Type Ic (SNeIc) produce the bulk of the observed long duration gamma-ray bursts (LGRBs), including high- and low-luminosity LGRBs and X-ray flashes, and if the LGRBs have the geometry assumed in the cannonball model of LGRBs, then their rate, measured by Swift, and their redshift distribution are consistent with the star formation rate (SFR) over the entire range of redshifts where the SFR has been measured with sufficient accuracy.

  8. On the Power Spectrum Density of Gamma Ray Bursts

    E-Print Network [OSTI]

    Motoko Suzuki; Masahiro Morikawa; Izumi Joichi

    2001-04-13T23:59:59.000Z

    Gamma ray bursts (GRBs) are known to have short-time variability and power-law behavior with the index -1.67 in the power spectrum density. Reanalyzing the expanded data, we have found a) the power-law comes from the global profile of the burst and not from the self-similar shots nor rapid fluctuations in the luminosity profile. b) The power indices vary from burst to burst and the value -1.67 is given simply as the mean value of the distribution; there is no systematic correlation among GRBs to yield the power law.

  9. Tail Emission of Prompt Gamma-Ray Burst Jets

    E-Print Network [OSTI]

    Yamazaki, R; Ioka, K; Nakamura, T; Yamazaki, Ryo; Toma, Kenji; Ioka, Kunihito; Nakamura, Takashi

    2006-01-01T23:59:59.000Z

    Tail emission of the prompt gamma-ray burst is discussed using a multiple emitting sub-shell (inhomogeneous jet, sub-jets) model. The tail is a superposition of a number of smooth, long-duration, dim, and soft pulses emitted by segments located far from the line of sight. We find that the behavior of the tail is not so much affected by the local inhomogeneity but affected by the global sub-jet distribution. Some observed tails may disfavor the power-law jets.

  10. Gamma-ray bursts and the sociology of science

    E-Print Network [OSTI]

    A. De Rujula

    2003-06-16T23:59:59.000Z

    I discuss what we have learned about Gamma-Ray Bursts (GRBs) by studying their `afterglows', and how these are interpreted in the generally-accepted `fireball' model of GRBs, as well as in the generally-unaccepted `cannonball' model of the same phenomena. The interpretation of GRBs is a good example around which to frame a discussion of the different approaches to science found in various fields, such as high-energy physics (HEP), high-energy astrophysics, or even the deciphering of ancient languages. I use this example to draw conclusions on `post-academic' science, and on the current status of European HEP.

  11. Gamma-Ray Bursts and Dark Matter - a joint origin?

    E-Print Network [OSTI]

    Daniel Enstrom

    1998-10-14T23:59:59.000Z

    A scenario is presented where large quark-gluon plasma (QGP) objects escaping the quark-hadron transition in the early Universe account for the baryonic dark matter as well as act as the sources for gamma-ray bursts. Two basic assumptions are made. Firstly, we assume that a QGP consisting of u,d and s quarks is the absolute ground state of QCD and secondly, that the quark-hadron transition in the early Universe was of first order. Both particle physics and astrophysics constraints are discussed, mainly from an observational point of view.

  12. Gamma-ray Bursts Produced by Mirror Stars

    E-Print Network [OSTI]

    S. Blinnikov

    1999-02-21T23:59:59.000Z

    I argue that cosmic Gamma-ray Bursts (GRB) may be produced by collapses or mergers of stars made of `mirror' matter. The mirror neutrinos (which are sterile for our matter) produced at these events can oscillate into ordinary neutrinos. The annihilations or decays of the latter create an electron-positron plasma and subsequent relativistic fireball with a very low baryon load needed for GRBs. The concept of mirror matter is able to explain several key problems of modern astrophysics: neutrino anomalies, the missing mass, MACHO microlensing events and GRBs. Thus this concept becomes very appealing and should be considered quite seriously and attentively.

  13. Gamma-Ray Bursts and Quantum Cosmic Censorship

    E-Print Network [OSTI]

    T. P. Singh

    1998-05-17T23:59:59.000Z

    Gamma-ray bursts are believed to result from the coalescence of binary neutron stars. However, the standard proposals for conversion of the gravitational energy to thermal energy have difficulties. We show that if the merger of the two neutron stars results in a naked singularity, instead of a black hole, the ensuing quantum particle creation can provide the requisite thermal energy in a straightforward way. The back-reaction of the created particles can avoid the formation of the naked singularity predicted by the classical theory. Hence cosmic censorship holds in the quantum theory, even if it were to be violated in classical general relativity.

  14. High Efficiency of Gamma-Ray Bursts Revisited

    E-Print Network [OSTI]

    Y. C. Zou; Z. G. Dai

    2007-03-07T23:59:59.000Z

    Using the conservation of energy and momentum during collisions of any two shells, we consider the efficiency of gamma-ray bursts by assuming that the ejecta from the central engine are equally massive and have the same Lorentz factors. We calculate the efficiency and the final Lorentz factor of the merged whole shell for different initial diversities of Lorentz factors and for different microscopic radiative efficiency. As a result, a common high efficiency in the range of 0.1 to 0.9 is considerable, and a very high value near 100% is also reachable if the diversity of the Lorentz factors is large enough.

  15. Virtual Gamma Ray Radiation Sources through Neutron Radiative Capture

    SciTech Connect (OSTI)

    Scott Wilde, Raymond Keegan

    2008-07-01T23:59:59.000Z

    The countrate response of a gamma spectrometry system from a neutron radiation source behind a plane of moderating material doped with a nuclide of a large radiative neutron capture cross-section exhibits a countrate response analogous to a gamma radiation source at the same position from the detector. Using a planar, surface area of the neutron moderating material exposed to the neutron radiation produces a larger area under the prompt gamma ray peak in the detector than a smaller area of dimensions relative to the active volume of the gamma detection system.

  16. Composite mirror facets for ground based gamma ray astronomy

    E-Print Network [OSTI]

    Brun, P; Durand, D; Glicenstein, J-F; Jeanney, C; Medina, M C; Micolon, P; Peyaud, B

    2013-01-01T23:59:59.000Z

    Composite mirrors for gamma-ray astronomy have been developed to fulfill the specifications required for the next generation of Cherenkov telescopes represented by CTA (Cherenkov Telescope Array). In addition to the basic requirements on focus and reflection efficiency, the mirrors have to be stiff, lightweight, durable and cost efficient. In this paper, the technology developed to produce such mirrors is described, as well as some tests that have been performed to validate them. It is shown that these mirrors comply with the needs of CTA, making them good candidates for use on a significant part of the array.

  17. Distance and spectrum of the Apollo gamma-ray burst

    SciTech Connect (OSTI)

    Gilman, D.; Metzger, A.E.; Parker, R.H.; Evans, L.G.; Trombka, J.I.

    1980-03-15T23:59:59.000Z

    The ..gamma..-ray spectrometer on Apollo 16 obtained spectral information with good energy resolution from more than 2500 burst photons in the energy range 0.06--5.16 MeV. The spectrum from 2 keV to 2 MeV, observed at X-ray energies by the Apollo X-ray spectrometer, is fitted by a thermal bremsstrahlung spectrum with kT=500 keV. The success of the fit implies that the source is optically thin, and it follows that it must be closer than 50 pc. Absence of spectral variability suggests that the burst results from isothermal changes in emission measure.

  18. Milagro: A TeV Gamma-Ray Monitor of the Northern Hemisphere Sky

    E-Print Network [OSTI]

    California at Santa Cruz, University of

    transients, such as gamma-ray bursts, and all sky surveys are diĆcult. A new type of TeV -ray observatoryMilagro: A TeV Gamma-Ray Monitor of the Northern Hemisphere Sky B.L. Dingus 1 , R. Atkins 1 , W type of very high energy (> a few 100 GeV) gamma-ray observatory, Milagro, has been built with a large

  19. Particle Acceleration and Gamma-ray emission due to magnetic reconnection in the core region of radio galaxies

    E-Print Network [OSTI]

    Khiali, Behrouz; Sol, Hélčne

    2015-01-01T23:59:59.000Z

    The current detectors of gamma-ray emission have too poor resolution to determine whether this emission is produced in the jet or in the core, specially of low luminous, non-blazar AGNs (as radio galaxies). In recent works it has been found that the power released by events of turbulent fast magnetic reconnection in the core region of these sources is more than sufficient to reproduce the observed gamma-ray luminosities. Besides, 3D MHD simulations with test particles have demonstrated that a first-order Fermi process within reconnection sites with embedded turbulence results very efficient particle acceleration rates. Employing this acceleration mechanism and the model above, and considering the relevant leptonic and hadronic loss processes in the core region, we computed the spectral energy distribution (SED) of radio galaxies for which very high energy (VHE) emission has been detected (namely, M87, Cen A, Per A, and IC 310). We found that these match very well specially with the VHE observations, therefore...

  20. Are Short and Long Gamma Ray Bursts Really of Different Origin?

    E-Print Network [OSTI]

    Ernst Karl Kunst

    2000-12-06T23:59:59.000Z

    It is shown that short and long gamma ray bursts (GRBs) are of the same origin and, furthermore, correlated with their duration.

  1. TPASS: a gamma-ray spectrum analysis and isotope identification computer code

    SciTech Connect (OSTI)

    Dickens, J.K.

    1981-03-01T23:59:59.000Z

    The gamma-ray spectral data-reduction and analysis computer code TPASS is described. This computer code is used to analyze complex Ge(Li) gamma-ray spectra to obtain peak areas corrected for detector efficiencies, from which are determined gamma-ray yields. These yields are compared with an isotope gamma-ray data file to determine the contributions to the observed spectrum from decay of specific radionuclides. A complete FORTRAN listing of the code and a complex test case are given.

  2. Swift Pointing and the Association Between Gamma-Ray Bursts and Gravitational-Wave Bursts

    E-Print Network [OSTI]

    Lee Samuel Finn; Badri Krishnan; Patrick J. Sutton

    2003-04-11T23:59:59.000Z

    The currently accepted model for gamma-ray burst phenomena involves the violent formation of a rapidly rotating solar mass black hole. Gravitational waves should be associated with the black-hole formation, and their detection would permit this model to be tested, the black hole progenitor (e.g., coalescing binary or collapsing stellar core) identified, and the origin of the gamma rays (within the expanding relativistic fireball or at the point of impact on the interstellar medium) located. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. To do any of these requires joint observations of gamma-ray burst events with gravitational and gamma-ray detectors. Here we examine how the quality of an upper limit on the gravitational-wave strength associated with gamma-ray burst observations depends on the relative orientation of the gamma-ray-burst and gravitational-wave detectors, and apply our results to the particular case of the Swift Burst-Alert Telescope (BAT) and the LIGO gravitational-wave detectors. A result of this investigation is a science-based ``figure of merit'' that can be used, together with other mission constraints, to optimize the pointing of the Swift telescope for the detection of gravitational waves associated with gamma-ray bursts.

  3. DETERMINATION OF THE POINT-SPREAD FUNCTION FOR THE FERMI LARGE AREA TELESCOPE FROM ON-ORBIT DATA AND LIMITS ON PAIR HALOS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect (OSTI)

    Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany)] [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M.; Allafort, A.; Bechtol, K.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)] [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan)] [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)] [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy)] [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France)] [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy)] [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy)] [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy)] [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T. J. [CNRS, IRAP, F-31028 Toulouse cedex 4 (France)] [CNRS, IRAP, F-31028 Toulouse cedex 4 (France); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy)] [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: mdwood@slac.stanford.edu, E-mail: mar0@uw.edu [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France); and others

    2013-03-01T23:59:59.000Z

    The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from Almost-Equal-To 20 MeV to >300 GeV. The pre-launch response functions of the LAT were determined through extensive Monte Carlo simulations and beam tests. The point-spread function (PSF) characterizing the angular distribution of reconstructed photons as a function of energy and geometry in the detector is determined here from two years of on-orbit data by examining the distributions of {gamma} rays from pulsars and active galactic nuclei (AGNs). Above 3 GeV, the PSF is found to be broader than the pre-launch PSF. We checked for dependence of the PSF on the class of {gamma}-ray source and observation epoch and found none. We also investigated several possible spatial models for pair-halo emission around BL Lac AGNs. We found no evidence for a component with spatial extension larger than the PSF and set upper limits on the amplitude of halo emission in stacked images of low- and high-redshift BL Lac AGNs and the TeV blazars 1ES0229+200 and 1ES0347-121.

  4. Probing Massive Stars Around Gamma-Ray Burst Progenitors

    E-Print Network [OSTI]

    Lu, Wenbin; Smoot, George F

    2015-01-01T23:59:59.000Z

    Long Gamma-Ray Bursts (GRBs) are produced by ultra-relativistic jets launched from core collapse of massive stars. Most massive stars form in binaries and/or in star clusters, which means that there may be a significant external photon field (EPF) around the GRB progenitor. We calculate the inverse-Compton scattering of EPF by the hot electrons in the GRB jet. Three possible cases of EPFs are considered: the progenitor is (I) in a massive binary system, (II) surrounded by a Wolf-Rayet-star wind, and (III) in a dense star cluster. Typical luminosities of 10^47 - 10^50 erg/s in the 10 - 100 GeV band are expected, depending on the stellar luminosity, binary separation (I), wind mass loss rate (II), stellar number density (III), etc. We calculate the lightcurve and spectrum in each case, taking fully into account the equal-arrival time surfaces and possible pair-production absorption with the prompt gamma-rays. Observations can put constraints on the existence of such EPFs (and hence on the nature of GRB progenit...

  5. The SKA view of Gamma-ray Bursts

    E-Print Network [OSTI]

    Burlon, Davide; van der Horst, Alexander; Murphy, Tara; Wijers, Ralph; Gaensler, Bryan; Ghisellini, Gabriele; Prandoni, Isabella

    2015-01-01T23:59:59.000Z

    Gamma-ray bursts (GRBs) are some of the most extreme events in the Universe. As well as providing a natural laboratory for investigating fundamental physical processes, they might trace the cosmic star formation rate up to extreme redshifts and probe the composition of the intergalactic medium over most of the Universe's history. Radio observations of GRBs play a key part in determining their physical properties, but currently they are largely limited to follow-up observations of $\\gamma$-ray-detected objects. The SKA will significantly increase our ability to study GRB afterglows, following up several hundred objects in the high frequency bands already in the "early science" implementation of the telescope. SKA1-MID Bands 4 (4 GHz) and 5 (9.2 GHz) will be particularly suited to the detection of these transient phenomena. The SKA will trace the peak of the emission, sampling the thick-to-thin transition of the evolving spectrum, and follow-up the afterglow down to the time the ejecta slow down to non-relativi...

  6. Uncovering the intrinsic variability of gamma-ray bursts

    SciTech Connect (OSTI)

    Golkhou, Vahid Z.; Butler, Nathaniel R., E-mail: vgolkhou@asu.edu, E-mail: natbutler@asu.edu [Cosmology Initiative, Arizona State University, Tempe, AZ 85287, USA. (United States)

    2014-05-20T23:59:59.000Z

    We develop a robust technique to determine the minimum variability timescale for gamma-ray burst (GRB) light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also retaining sensitivity to narrow pulses within complicated time series. In contrast to previous studies using wavelets, which simply define the minimum timescale in reference to the measurement noise floor, our approach identifies the signature of temporally smooth features in the wavelet scaleogram and then additionally identifies a break in the scaleogram on longer timescales as a signature of a true, temporally unsmooth light curve feature or features. We apply our technique to the large sample of Swift GRB gamma-ray light curves and for the first time—due to the presence of a large number of GRBs with measured redshift—determine the distribution of minimum variability timescales in the source frame. We find a median minimum timescale for long-duration GRBs in the source frame of ?t {sub min} = 0.5 s, with the shortest timescale found being on the order of 10 ms. This short timescale suggests a compact central engine (3 × 10{sup 3} km). We discuss further implications for the GRB fireball model and present a tantalizing correlation between the minimum timescale and redshift, which may in part be due to cosmological time dilation.

  7. Gamma Ray Array Detector Trigger Sub-System

    E-Print Network [OSTI]

    Du Zhong-Wei; Su Hong; Qian Yi; Kong Jie

    2013-05-19T23:59:59.000Z

    Gamma Ray Array Detector (GRAD) is one of External Target Facility (ETF) subsystems at the Heavy Ion Research Facility at Lanzhou. The trigger subsystem of the GRAD has been developed based on Field Programmable Gate Array (FPGAs) and PXI interface. The GRAD trigger subsystem makes prompt L1 trigger decisions to select valid events. These decisions are made by processing the hit signals from 1024 CsI scintillators of the GRAD. According to the physical requirements, the GRAD trigger subsystem generates 12-bit trigger signals that are passed to the ETF global trigger system. In addition, the GRAD trigger subsystem generates trigger data that are packed and transmitted to the host computer via PXI bus for off-line analysis. The trigger processing is implemented in the front-end electronics and one FPGA of the trigger module. The logic of PXI transmission and reconfiguration is implemented in the other FPGA of the trigger module. The reliable and efficient performance in the Gamma-ray experiments demonstrates that the GRAD trigger subsystem is capable to satisfy the physical requirements.

  8. Gamma ray-induced embrittlement of pressure vessel alloys

    SciTech Connect (OSTI)

    Alexander, D.E.; Rehn, L.E. [Argonne National Lab., IL (United States); Farrell, K.; Stoller, R.E. [Oak Ridge National Lab., TN (United States)

    1994-11-01T23:59:59.000Z

    High-energy gamma rays emitted from the core of a nuclear reactor produce displacement damage in the reactor pressure vessel (RPV). The contribution of gamma damage to RPV embrittlement has in the past been largely ignored. However, in certain reactor designs the gamma flux at the RPV is sufficiently large that its contribution to displacement damage can be substantial. For example, gamma rays have been implicated in the accelerated RPV embrittlement observed in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. In the present study, mechanical property changes induced by 10-MeV electron irradiation of a model Fe alloy and an RPV alloy of interest to the HFIR were examined. Mini-tensile specimens were irradiated with high-energy electrons to reproduce damage characteristic of the Compton recoil-electrons induced by gamma bombardment. Substantial increases in yield and ultimate stress were observed in the alloys after irradiation to doses up to 5.3x10{sup {minus}3} dpa at temperatures ({approximately}50{degrees}C) characteristic of the HFIR pressure vessel. These measured increases were similar to those previously obtained following neutron irradiation, despite the highly disparate nature of the damage generated during electron and neutron irradiation.

  9. Neutrino Emission from Gamma-Ray Burst Fireballs, Revised

    E-Print Network [OSTI]

    Svenja Hümmer; Philipp Baerwald; Walter Winter

    2012-05-02T23:59:59.000Z

    We review the neutrino flux from gamma-ray bursts, which is estimated from gamma-ray observations and used for the interpretation of recent IceCube data, from a particle physics perspective. We numerically calculate the neutrino flux for the same astrophysical assumptions as the analytical fireball neutrino model, including the dominant pion and kaon production modes, flavor mixing, and magnetic field effects on the secondary muons, pions, and kaons. We demonstrate that taking into account the full energy dependencies of all spectra, the normalization of the expected neutrino flux reduces by about one order of magnitude and the spectrum shifts to higher energies, where we can pin down the exact origin of the discrepancies by the re-computation of the analytical models. We also reproduce the IceCube-40 analysis for exactly the same bursts and same assumptions and illustrate the impact of uncertainties. We conclude that the baryonic loading of the fireballs, which is an important control parameter for the emission of cosmic rays, can be constrained significantly with the full-scale experiment after about ten years.

  10. Prospects for joint gravitational wave and short gamma-ray burst observations

    E-Print Network [OSTI]

    J. Clark; H. Evans; S. Fairhurst; I. W. Harry; E. Macdonald; D. Macleod; P. J. Sutton; A. R. Williamson

    2014-09-29T23:59:59.000Z

    We present a detailed evaluation of the expected rate of joint gravitational-wave and short gamma-ray burst (GRB) observations over the coming years. We begin by evaluating the improvement in distance sensitivity of the gravitational wave search that arises from using the GRB observation to restrict the time and sky location of the source. We argue that this gives a 25% increase in sensitivity when compared to an all-sky, all-time search, corresponding to more than doubling the number of detectable gravitational wave signals associated with GRBs. Using this, we present the expected rate of joint observations with the advanced LIGO and Virgo instruments, taking into account the expected evolution of the gravitational wave detector network. We show that in the early advanced gravitational wave detector observing runs, from 2015-2017, there is only a small chance of a joint observation. However, as the detectors approach their design sensitivities, there is a good chance of joint observations provided wide field GRB satellites, such as Fermi and the Interplanetary Network, continue operation. The rate will also depend critically upon the nature of the progenitor, with neutron star--black hole systems observable to greater distances than double neutron star systems. The relative rate of binary mergers and GRBs will depend upon the jet opening angle of GRBs. Consequently, joint observations, as well as accurate measurement of both the GRB rate and binary merger rates will allow for an improved estimation of the opening angle of GRBs.

  11. ON THE ORIGIN OF > 10 GeV PHOTONS IN GAMMA-RAY BURST AFTERGLOWS

    SciTech Connect (OSTI)

    Wang Xiangyu; Liu Ruoyu [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Lemoine, Martin [Institut d'Astrophysique de paris, CNRS, UPMC, 98 bis boulevard Arago, F-75014 Paris (France)

    2013-07-10T23:59:59.000Z

    Fermi/LAT has detected long-lasting high-energy photons (>100 MeV) from gamma-ray bursts (GRBs), with the highest energy photons reaching about 100 GeV. One proposed scenario is that they are produced by high-energy electrons accelerated in GRB forward shocks via synchrotron radiation. We study the maximum synchrotron photon energy in this scenario, considering the properties of the microturbulence magnetic fields behind the shock, as revealed by recent particle-in-cell simulations and theoretical analyses of relativistic collisionless shocks. Due to the small-scale nature of the microturbulent magnetic field, the Bohm acceleration approximation, in which the scattering mean free path is equal to the particle Larmor radius, breaks down at such high energies. This effect leads to a typical maximum synchrotron photon of a few GeV at 100 s after the burst and this maximum synchrotron photon energy decreases quickly with time. We show that the fast decrease of the maximum synchrotron photon energy leads to a fast decay of the synchrotron flux. The 10-100 GeV photons detected after the prompt phase cannot be produced by the synchrotron mechanism. They could originate from the synchrotron self-Compton emission of the early afterglow if the circumburst density is sufficiently large, or from the external inverse Compton process in the presence of central X-ray emission, such as X-ray flares and prompt high-latitude X-ray emission.

  12. A SEARCH FOR PULSATIONS IN SHORT GAMMA-RAY BURSTS TO CONSTRAIN THEIR PROGENITORS

    SciTech Connect (OSTI)

    Dichiara, S.; Guidorzi, C.; Frontera, F. [Department of Physics and Earth Sciences, University of Ferrara, via Saragat 1, I-44122 Ferrara (Italy); Amati, L. [INAF-IASF Bologna, via Gobetti 101, I-40129 Bologna (Italy)

    2013-11-10T23:59:59.000Z

    We searched for periodic and quasi-periodic signals in the prompt emission of a sample of 44 bright short gamma-ray bursts (GRBs) detected with Fermi/GBM, Swift/BAT, and CGRO/BATSE. The aim was to look for the observational signature of quasi-periodic jet precession, which is expected from black hole (BH)-neutron star (NS) mergers, but not from double NS systems. Thus, this kind of search holds the key to identifying the progenitor systems of short GRBs and, in the interim before gravitational wave detectors become on-lines, represents the only direct way to constrain the progenitors. We tailored our search to the nature of the expected signal by properly stretching the observed light curves by an increasing factor with time, after calibrating the technique with synthetic curves. None of our GRBs showed evidence for periodic or quasi-periodic signals. In particular, for the seven unambiguously short GRBs with the best signal-to-noise ratios, we obtained significant upper limits to the amplitude of the possible oscillations. This result suggests that BH-NS systems do not dominate the population of short GRB progenitors, as described by the kinematic model of Stone et al.

  13. 'Self-absorbed' GeV light curves of gamma-ray burst afterglows

    SciTech Connect (OSTI)

    Panaitescu, A.; Vestrand, W. T.; Wo?niak, P. [Space and Remote Sensing, MS B244, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2014-06-10T23:59:59.000Z

    We investigate the effect that the absorption of high-energy (above 100 MeV) photons produced in gamma-ray burst afterglow shocks has on the light curves and spectra of Fermi Large Area Telescope (LAT) afterglows. Afterglows produced by the interaction of a relativistic outflow with a wind-like medium peak when the blast wave deceleration sets in, and the afterglow spectrum could be hardening before that peak, as the optical thickness to pair formation is decreasing. In contrast, in afterglows produced in the interaction with a homogeneous medium, the optical thickness to pair formation should increase and yield a light curve peak when it reaches unity, followed by a fast light curve decay, accompanied by spectral softening. If energy is injected in the blast wave, then the accelerated increase of the optical thickness yields a convex afterglow light curve. Other features, such as a double-peak light curve or a broad hump, can arise from the evolution of the optical thickness to photon-photon absorption. Fast decays and convex light curves are seen in a few LAT afterglows, but the expected spectral softening is rarely seen in (and difficult to measure with) LAT observations. Furthermore, for the effects of photon-photon attenuation to shape the high-energy afterglow light curve without attenuating it too much, the ejecta initial Lorentz factor must be in a relatively narrow range (50-200), which reduces the chance of observing those effects.

  14. Simulation and physical model based gamma-ray burst afterglow analysis

    E-Print Network [OSTI]

    van Eerten, Hendrik

    2015-01-01T23:59:59.000Z

    Advances in our numerical and theoretical understanding of gamma-ray burst afterglow processes allow us to construct models capable of dealing with complex relativistic jet dynamics and non-thermal emission, that can be compared directly to data from instruments such as Swift. Because afterglow blast waves and power law spectra are intrinsically scale-invariant under changes of explosion energy and medium density, templates can be generated from large-scale hydrodynamics simulations. This allows for iterative template-based model fitting using the physical model parameters (quantifying the properties of the burster, emission and observer) directly as fit variables. Here I review how such an approach to afterglow analysis works in practice, paying special attention to the underlying model assumptions, possibilities, caveats and limitations of this type of analysis. Because some model parameters can be degenerate in certain regions of parameter space, or unconstrained if data in a limited number of a bands is a...

  15. Nucleosynthesis of Nickel-56 from Gamma-Ray Burst Accretion Disks

    E-Print Network [OSTI]

    R. Surman; G. C. McLaughlin; N. Sabbatino

    2011-12-12T23:59:59.000Z

    We examine the prospects for producing Nickel-56 from black hole accretion disks, by examining a range of steady state disk models. We focus on relatively slowly accreting disks in the range of 0.05 - 1 solar masses per second, as are thought to be appropriate for the central engines of long-duration gamma-ray bursts. We find that significant amounts of Nickel-56 are produced over a wide range of parameter space. We discuss the influence of entropy, outflow timescale and initial disk position on mass fraction of Nickel-56 which is produced. We keep careful track of the weak interactions to ensure reliable calculations of the electron fraction, and discuss the role of the neutrinos.

  16. Constraining the Lorentz invariance violation from the continuous spectra of short gamma-ray bursts

    E-Print Network [OSTI]

    Chang, Zhe; Lin, Hai-Nan; Sang, Yu; Wang, Ping; Wang, Sai

    2015-01-01T23:59:59.000Z

    In quantum gravity, a foamy structure of space-time leads to Lorentz invariance violation (LIV). As the most energetic astrophysical processes in the Universe, gamma-ray bursts (GRBs) provide an effective way to probe quantum gravity effects. We use continuous spectra of 20 short GRBs detected by the Swift satellite to give a conservative lower limit of quantum gravity energy scale $M_\\textrm{QG} $. Due to the LIV effect, photons with different energy have different velocities. This will lead to the delayed arrival of high energy photons relative to the low energy ones. Based on the fact that the LIV-induced time delay can't be longer than the duration of a GRB, we present the most conservative estimation of the quantum gravity energy scales from 20 short GRBs. The most strict constraint, $M_\\textrm{QG}>5.05\\times10^{14}$ GeV, is from GRB 140622A.

  17. Extending the Fermi-LAT Data Processing Pipeline to the Grid

    E-Print Network [OSTI]

    Stephan Zimmer; Luisa Arrabito; Tom Glanzman; Tony Johnson; Claudia Lavalley; Andrei Tsaregorodtsev

    2012-12-17T23:59:59.000Z

    The Data Handling Pipeline ("Pipeline") has been developed for the Fermi Gamma-Ray Space Telescope (Fermi) Large Area Telescope (LAT) which launched in June 2008. Since then it has been in use to completely automate the production of data quality monitoring quantities, reconstruction and routine analysis of all data received from the satellite and to deliver science products to the collaboration and the Fermi Science Support Center. Aside from the reconstruction of raw data from the satellite (Level 1), data reprocessing and various event-level analyses are also reasonably heavy loads on the pipeline and computing resources. These other loads, unlike Level 1, can run continuously for weeks or months at a time. In addition it receives heavy use in performing production Monte Carlo tasks. The software comprises web-services that allow online monitoring and provides charts summarizing work flow aspects and performance information. The server supports communication with several batch systems such as LSF and BQS and recently also Sun Grid Engine and Condor. This is accomplished through dedicated job control services that for Fermi are running at SLAC and the other computing site involved in this large scale framework, the Lyon computing center of IN2P3. While being different in the logic of a task, we evaluate a separate interface to the Dirac system in order to communicate with EGI sites to utilize Grid resources, using dedicated Grid optimized systems rather than developing our own. (abstract abridged)

  18. Search for gamma-rays from the unusually bright GRB 130427A with the HAWC Gamma-ray Observatory

    E-Print Network [OSTI]

    Abeysekara, A U; Alvarez, C; Arceo, R; Arteaga-Velázquez, J C; Solares, H A Ayala; Barber, A S; Baughman, B M; Bautista-Elivar, N; BenZvi, S Y; Rosales, M Bonilla; Braun, J; Caballero-Mora, K S; Carramińana, A; Castillo, M; Cotti, U; Cotzomi, J; de la Fuente, E; De León, C; DeYoung, T; Hernandez, R Diaz; Dingus, B L; DuVernois, M A; Ellsworth, R W; Fiorino, D W; Fraija, N; Galindo, A; González, M M; Goodman, J A; Gussert, M; Hampel-Arias, Z; Harding, J P; Hui, C M; Hüntemeyer, P; Imran, A; Iriarte, A; Karn, P; Kieda, D; Kunde, G J; Lara, A; Lauer, R J; Lee, W H; Lennarz, D; Vargas, H León; Linnemann, J T; Longo, M; Luna-García, R; Malone, K; Marinelli, A; Marinelli, S S; Martinez, H; Martinez, O; Martínez-Castro, J; Matthews, J A J; Torres, E Mendoza; Miranda-Romagnoli, P; Moreno, E; Mostafá, M; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T O; Patricelli, B; Pelayo, R; Ponce, E; Pretz, J; Pérez-Pérez, E G; Rivičre, C; Rosa-González, D; Salazar, H; Greus, F Salesa; Sandoval, A; Schneider, M; Sinnis, G; Smith, A J; Woodle, K Sparks; Springer, R W; Taboada, I; Tollefson, K; Torres, I; Ukwatta, T N; Villaseńor, L; Weisgarber, T; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Younk, P W; Zaborov, D; Zepeda, A; Zhou, H; Álvarez, J D

    2014-01-01T23:59:59.000Z

    The long gamma-ray burst (GRB) 130427A was the most powerful burst ever detected with a redshift $z\\lesssim0.5$, featuring the highest energy photon so far detected from a GRB and the longest lasting emission above 100 MeV. The HAWC Gamma-ray Observatory is a new extensive air shower detector currently under construction in central Mexico. It features two data acquisition (DAQ) systems - one designed to readout full air-shower events (main DAQ) and the other one counting the signals in each photomultiplier tube (scaler DAQ). The burst occurred at a zenith angle of $57^\\circ$, when HAWC was running 10% of the final detector and collecting data with the scaler DAQ only. Based on the observed light curve at MeV-GeV energies, 8 different time periods have been searched for prompt and delayed emission from this GRB. In all cases, no statistically significant excess of counts has been found and upper limits have been placed. It is shown that a similar GRB close to zenith would be easily detected by the full HAWC de...

  19. DELAYED ONSET OF HIGH-ENERGY EMISSIONS IN LEPTONIC AND HADRONIC MODELS OF GAMMA-RAY BURSTS

    SciTech Connect (OSTI)

    Asano, Katsuaki [Interactive Research Center of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Meszaros, Peter, E-mail: asano@phys.titech.ac.jp, E-mail: nnp@astro.psu.edu [Department of Astronomy and Astrophysics, Department of Physics, Center for Particle and Gravitational Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

    2012-10-01T23:59:59.000Z

    The temporal-spectral evolution of the prompt emission of gamma-ray bursts is simulated numerically for both leptonic and hadronic models. For weak enough magnetic fields, leptonic models can reproduce the few seconds delay of the onset of GeV photon emission observed by Fermi-LAT, due to the slow growth of the target photon field for inverse Compton scattering. For stronger magnetic fields, the GeV delay can be explained with hadronic models, due to the long acceleration timescale of protons and the continuous photopion production after the end of the particle injection. While the FWHMs of the MeV and GeV light curves are almost the same in one-zone leptonic models, the FWHMs of the 1-30 GeV light curves in hadronic models are significantly wider than those of the 0.1-1 MeV light curves. The amount of the GeV delay depends on the importance of the Klein-Nishina effect in both the leptonic and hadronic models. In our examples of hadronic models the energies of the escaped neutrons are comparable to the gamma-ray energy, although their contribution to the ultra high-energy cosmic rays is still subdominant. The resulting neutrino spectra are hard enough to avoid the flux limit constraint from IceCube. The delay of the neutrino emission onset is up to several times longer than the corresponding delay of the GeV photon emission onset. The quantitative differences in the light curves for various models may be further tested with future atmospheric Cerenkov telescopes whose effective area is larger than that of Fermi-LAT, such as CTA.

  20. Gamma Ray Burst Section of the White Paper on the Status and Future of Ground-based TeV Gamma-ray Astronomy

    E-Print Network [OSTI]

    Falcone, A D; Baring, M G; Blandford, R; Buckley, J; Connaughton, V; Coppi, P; Dermer, C; Dingus, B; Fryer, C; Gehrels, N; Granot, J; Horan, D; Katz, J I; Kühn, K; Mészáros, P; Norris, J; Parkinson, P Saz; Peér, A; Ramirez-Ruiz, E; Razzaque, S; Wang, X Y; Zhang, B

    2008-01-01T23:59:59.000Z

    This is a report on the findings of the gamma ray burst working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses the status of past and current attempts to observe gamma ray bursts at GeV-TeV energies. We concentrate on the potential of future ground-based gamma-ray experiments to observe the highest energy emission ever recorded for GRBs, particularly for those that are nearby and have high Lorentz factors in the GRB jet. It is clear that major advances are possible and that the detection of very high energy emission would have strong implications for GRB models, as well as cosmic ray origin.