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1

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

SciTech Connect

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.

Grenier, Isabelle (University Paris Diderot and CEA Saclay, France)

2009-04-01T23:59:59.000Z

2

SLAC National Accelerator Laboratory - Fermi's Latest Gamma-ray...  

NLE Websites -- All DOE Office Websites (Extended Search)

Fermi's Latest Gamma-ray Census Highlights Cosmic Mysteries By Francis Reddy, NASAGoddard Space Flight Center September 9, 2011 Every three hours, NASA's Fermi Gamma-ray Space...

3

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

E-Print Network (OSTI)

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.

Luca Baldini for the Fermi LAT Collaboration

2011-01-09T23:59:59.000Z

4

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

SciTech Connect

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.

Bloom, Elliott (SLAC)

2011-03-30T23:59:59.000Z

5

Fermi Observations of Gamma?ray Bursts  

Science Conference Proceedings (OSTI)

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

Masanori Ohno; The Fermi?LAT collaborations; The GBM collaborations

2010-01-01T23:59:59.000Z

6

79Fermi Observatory Measures the Lumps in Space An artistic impression of two gamma-ray photons  

E-Print Network (OSTI)

explored to date. As the gamma-rays travel through space, the shortest-wavelength gamma-rays take? Problem 3 ­ The Fermi Telescope measured a gamma-ray pulse from a distant object located 10 billion light from a distant object located 10 billion light years from Earth. The time delay was no more than 0

7

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

E-Print Network (OSTI)

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.

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

2010-10-31T23:59:59.000Z

8

The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission  

SciTech Connect

The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy {gamma}-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy {gamma}-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (4) localize point sources to 0.3-2 arcmin, (5) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (6) measure the diffuse isotropic {gamma}-ray background up to TeV energies, and (7) explore the discovery space for dark matter.

Atwood, W.B.; /UC, Santa Cruz; Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Anderson, B. /UC, Santa Cruz; Axelsson, M.; /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Band, D.L.; /NASA, Goddard /NASA, Goddard; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bartelt, J.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bederede, D.; /DAPNIA, Saclay; Bellardi, F.; /INFN, Pisa; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bignami, G.F.; /Pavia U.; Bisello, D.; /INFN, Padua /Padua U.; Bissaldi, E.; /Garching, Max Planck Inst., MPE; Blandford, R.D.; /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. /INFN, Perugia /Perugia U. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Pisa /INFN, Pisa /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /INFN, Padua /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /Kalmar U. /Royal Inst. Tech., Stockholm /DAPNIA, Saclay /ASI, Rome /INFN, Pisa /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. /DAPNIA, Saclay /NASA, Goddard /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

2009-05-15T23:59:59.000Z

9

Fermi Observations of Gamma-ray Bursts  

SciTech Connect

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.

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

10

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

SciTech Connect

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.

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

11

Gamma-ray astronomy: From Fermi up to the HAWC high-energy {gamma}-ray observatory in Sierra Negra  

SciTech Connect

Gamma-rays represent the most energetic electromagnetic window for the study of the Universe. They are studied both from space at MeV and GeV energies, with instruments like the Fermi{gamma}-ray Space Telescope, and at TeV energies with ground based instruments profiting of particle cascades in the atmosphere and of the Cerenkov radiation of charged particles in the air or in water. The Milagro gamma-ray observatory represented the first instrument to successfully implement the water Cerenkov technique for {gamma}-ray astronomy, opening the ground for the more sensitive HAWC {gamma}-ray observatory, currently under development in the Sierra Negra site and already providing early science results.

Carraminana, Alberto [Instituto Nacional de Astrofisica, Optica y Electronica Luis Enrique Erro 1, Tonantzintla, Puebla 72840 (Mexico); Collaboration: HAWC Collaboration

2013-06-12T23:59:59.000Z

12

GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky |  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky GLAST Observatory Renamed for Fermi, Reveals Entire Gamma-Ray Sky August 26, 2008 - 3:20pm Addthis WASHINGTON, D.C. - The U.S. Department of Energy (DOE) and NASA announced today that the Gamma-Ray Large Area Space Telescope (GLAST) has revealed its first all-sky map in gamma rays. The onboard Large Area Telescope's (LAT) all-sky image-which shows the glowing gas of the Milky Way, blinking pulsars and a flaring galaxy billions of light-years away-was created using only 95 hours of "first light" observations, compared with past missions which took years to produce a similar image. Scientists expect the telescope will discover many new pulsars in our own galaxy, reveal powerful

13

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

E-Print Network (OSTI)

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).

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

14

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

SciTech Connect

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.

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

15

Fermi GBM Observations of Terrestrial Gamma-ray Flashes  

Science Conference Proceedings (OSTI)

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.

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

2011-09-21T23:59:59.000Z

16

Gamma-Rays from Radio Galaxies: Fermi-Lat Observations  

E-Print Network (OSTI)

We review the high energy properties of Misaligned AGNs associated with gamma-ray sources detected by Fermi in 24 months of survey. Most of them are nearby emission low power radio galaxies (i.e FRIs) which probably have structured jets. On the contrary, high power radio sources (i.e FRIIs) with GeV emission are rare. The small number of FRIIs does not seem to be related to their higher redshifts. Assuming proportionality between the radio core flux and the gamma-ray flux, several of them are expected to be bright enough to be detected above 100 MeV in spite of their distance. We suggest that beaming/jet structural differences are responsible for the detection rate discrepancy observed between FRIs and FRIIs.

Grandi, Paola

2011-01-01T23:59:59.000Z

17

Fermi-LAT and the Gamma-Ray Line Search  

E-Print Network (OSTI)

A distinct signature for dark matter in the form of weakly interacting massive particles (WIMPs) would be the detection of a monochromatic spectral line in the gamma-ray sky. The Fermi-LAT collaboration has searched for such a line in the energy range from 5 to 300 GeV in five sky regions around the Galactic centre. No globally significant line is detected, and 95% CL upper limits on monochromatic-line strengths are presented. The smallest search region reveals a line-like structure at 133 GeV with a local significance of 2.9 sigma after 4.4 years of data, which translates to less than 1 sigma global significance from a trial factor of around 200.

Gustafsson, Michael

2013-01-01T23:59:59.000Z

18

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

SciTech Connect

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.

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

19

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

SciTech Connect

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.

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

20

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

SciTech Connect

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.

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

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21

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

Science Conference Proceedings (OSTI)

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.

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

22

Gamma-ray burst observations with new generation imaging atmospheric Cerenkov Telescopes in the FERMI era  

SciTech Connect

After the launch and successful beginning of operations of the FERMI satellite, the topics related to high-energy observations of gamma-ray bursts have obtained a considerable attention by the scientific community. Undoubtedly, the diagnostic power of high-energy observations in constraining the emission processes and the physical conditions of gamma-ray burst is relevant. We briefly discuss how gamma-ray burst observations with ground-based imaging array Cerenkov telescopes, in the GeV-TeV range, can compete and cooperate with FERMI observations, in the MeV-GeV range, to allow researchers to obtain a more detailed and complete picture of the prompt and afterglow phases of gamma-ray bursts.

Covino, S.; Campana, S. [INAF/Brera Astronomical Observatory, Via Bianchi 46, 23807, Merate (Saint Lucia) (Italy); Garczarczyk, M. [Max-Planck-Institut fuer Physik, Foehringer Ring 6, D-80805 Muenchen (Germany); IFAE, Edifici Cn., Campus UAB, 08193 Bellaterra (Spain); Galante, N. [Max-Planck-Institut fuer Physik, Foehringer Ring 6, D-80805 Muenchen (Germany); Gaug, M. [Instituto de Astrofisica de Canarias, via Lactea s/n, 38205 La Laguna, Tenerife (Spain); Antonelli, A. [INAF/Rome Astronomical Observatory, Via Frascati 33, 00044, Monte Porzio (Roma) (Italy); Bastieri, D. [Universita di Padova and Istituto Nazionale di Fisica Nucleare (INFN), 35131, Padova (Italy); Longo, F. [Dipartimento Fisica and INFN Trieste, 34127 Trieste (Italy); Scapin, V. [Universita di Udine, and INFN Trieste, 33100 Udine (Italy)

2009-04-08T23:59:59.000Z

23

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

SciTech Connect

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.

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

24

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

SciTech Connect

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.

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

25

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

E-Print Network (OSTI)

; 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

Pasko, Victor

26

All-Sky Earth Occultation Observations with the Fermi Gamma Ray Burst Monitor  

E-Print Network (OSTI)

Using the Gamma Ray Burst Monitor (GBM) on-board Fermi, we are monitoring the hard X-ray/soft gamma ray sky using the Earth occultation technique. Each time a source in our catalog enters or exits occultation by the Earth, we measure its flux using the change in count rates due to the occultation. Currently we are using CTIME data with 8 energy channels spanning 8 keV to 1 MeV for the GBM NaI detectors and spanning 150 keV to 40 MeV for the GBM BGO detectors. Our preliminary catalog consists of galactic X-ray binaries, the Crab Nebula, and active galactic nuclei. In addition, to Earth occultations, we have observed numerous occultations with Fermi's solar panels. We will present early results. Regularly updated results can be found on our website http://gammaray.nsstc.nasa.gov/gbm/science/occultation

Wilson-Hodge, Colleen A; Bhat, P N; Briggs, M S; Chaplin, V; Connaughton, V; Camero-Arranz, A; Case, G; Cherry, M; Rodi, J; Finger, M H; Jenke, P; Haynes, R H

2009-01-01T23:59:59.000Z

27

THE FERMI GBM GAMMA-RAY BURST SPECTRAL CATALOG: THE FIRST TWO YEARS  

Science Conference Proceedings (OSTI)

We present systematic spectral analyses of gamma-ray bursts (GRBs) detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first two years of operation. This catalog contains two types of spectra extracted from 487 GRBs, and by fitting four different spectral models, this results in a compendium of over 3800 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 procedure 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 Fermi GBM Science Team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.

Goldstein, Adam; Burgess, J. Michael; Preece, Robert D.; Briggs, Michael S.; Guiriec, Sylvain; Connaughton, Valerie; Paciesas, William S.; Bhat, P. N.; Chaplin, Vandiver [Physics Department, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Van der Horst, Alexander J.; Meegan, Charles A. [Universities Space Research Association, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Wilson-Hodge, Colleen A.; Fishman, Gerald J. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Von Kienlin, Andreas; Bissaldi, Elisabetta; Diehl, Roland; Foley, Suzanne [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 [Jacobs Technology, 1500 Perimeter Parkway, Huntsville, AL 35806 (United States); and others

2012-03-01T23:59:59.000Z

28

Fermi Limit on the Neutrino Flux from Gamma-ray Bursts  

E-Print Network (OSTI)

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.

Zhuo Li

2012-10-24T23:59:59.000Z

29

Tentative observation of a gamma-ray line at the Fermi LAT  

E-Print Network (OSTI)

Using 43 months of public gamma-ray data from the Fermi Large Area Telescope, we find in regions close to the Galactic center at energies of 130 GeV a 4.6 sigma excess that is not inconsistent with a gamma-ray line from dark matter annihilation. When taking into account the look-elsewhere effect, the significance of the observed signature is 3.2 sigma. If interpreted in terms of dark matter particles annihilating into a photon pair, the observations imply a partial annihilation cross-section of about 10^-27 cm^3s^-1 and a dark matter mass around 130 GeV. We review aspects of the statistical analysis and comment on possible instrumental indications.

Weniger, Christoph

2012-01-01T23:59:59.000Z

30

FERMI LIMIT ON THE NEUTRINO FLUX FROM GAMMA-RAY BURSTS  

SciTech Connect

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.

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

31

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

Science Conference Proceedings (OSTI)

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.

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

32

Population Synthesis of Radio and Gamma-ray Pulsars in the Fermi Era  

E-Print Network (OSTI)

We present results of our pulsar population synthesis of normal pulsars from the Galactic disk using our previously developed computer code. On the same footing, we use slot gap and outer gap models for gamma-ray emission from normal pulsars to obtain statistics of radio-loud and radio-quiet gamma-ray pulsars. From recently improved understanding of HII and star forming regions in the Galaxy, we develop a new surface density model of the birth location of neutron stars. We explore models of neutron star evolution with magnetic field-decay, and with different initial period and magnetic field distributions. We present preliminary results including simulated population statistics that are compared with recent detections by Fermi of normal, isolated pulsars.

Gonthier, Peter L; Harding, Alice K; Grenier, Isabelle A; Pierbattista, Marco

2011-01-01T23:59:59.000Z

33

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

SciTech Connect

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.

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

34

Luminosities and Space Densities of Short Gamma-Ray Bursts  

E-Print Network (OSTI)

Using the Euclidean value of as a cosmological distance indicator, we derive the isotropic-equivalent characteristic peak luminosity of gamma-ray bursts both longer and shorter than 2 s. The short bursts have essentially the same characteristic peak luminosity of 0.6 x 10^51 erg (0.064s)^-1 as do the long bursts. This may apply also to bursts with durations less than 0.25 s. The local space density of short bursts is around three times lower than that of long bursts.

Maarten Schmidt

2001-08-29T23:59:59.000Z

35

Discovery of Nine Gamma-Ray Pulsars in Fermi-LAT Data Using a New Blind Search Method  

E-Print Network (OSTI)

We report the discovery of nine previously unknown gamma-ray pulsars in a blind search of data from the Fermi Large Area Telescope (LAT). The pulsars were found with a novel hierarchical search method originally developed for detecting continuous gravitational waves from rapidly rotating neutron stars. Designed to find isolated pulsars spinning at up to kHz frequencies, the new method is computationally efficient, and incorporates several advances, including a metric-based gridding of the search parameter space (frequency, frequency derivative and sky location) and the use of photon probability weights. The nine pulsars have spin frequencies between 3 and 12 Hz, and characteristic ages ranging from 17 kyr to 3 Myr. Two of them, PSRs J1803-2149 and J2111+4606, are young and energetic Galactic-plane pulsars (spin-down power above 6e35 erg/s and ages below 100 kyr). The seven remaining pulsars, PSRs J0106+4855, J0622+3749, J1620-4927, J1746-3239, J2028+3332, J2030+4415, J2139+4716, are older and less energetic; two of them are located at higher Galactic latitudes (|b| > 10 deg). PSR J0106+4855 has the largest characteristic age (3 Myr) and the smallest surface magnetic field (2e11 G) of all LAT blind-search pulsars. PSR J2139+4716 has the lowest spin-down power (3e33 erg/s) among all non-recycled gamma-ray pulsars ever found. Despite extensive multi-frequency observations, only PSR J0106+4855 has detectable pulsations in the radio band. The other eight pulsars belong to the increasing population of radio-quiet gamma-ray pulsars.

H. J. Pletsch; L. Guillemot; B. Allen; M. Kramer; C. Aulbert; H. Fehrmann; P. S. Ray; E. D. Barr; A. Belfiore; F. Camilo; P. A. Caraveo; O. Celik; D. J. Champion; M. Dormody; R. P. Eatough; E. C. Ferrara; P. C. C. Freire; J. W. T. Hessels; M. Keith; M. Kerr; A. de Luca; A. G. Lyne; M. Marelli; M. A. McLaughlin; D. Parent; S. M. Ransom; M. Razzano; W. Reich; P. M. Saz Parkinson; B. W. Stappers; M. T. Wolff

2011-11-02T23:59:59.000Z

36

The Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived From First-Year Fermi Large Area Telescope Data  

SciTech Connect

We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called 'extra-galactic' diffuse {gamma}-ray emission (EGB). This component of the diffuse {gamma}-ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modelling of the bright foreground diffuse Galactic {gamma}-ray emission (DGE), the detected LAT sources and the solar {gamma}-ray emission. We find the spectrum of the EGB is consistent with a power law with differential spectral index {gamma} = 2.41 {+-} 0.05 and intensity, I(> 100 MeV) = (1.03 {+-} 0.17) x 10{sup -5} cm{sup -2} s{sup -1} sr{sup -1}, where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.

Abdo, A. A.

2011-08-19T23:59:59.000Z

37

EVIDENCE FOR INDIRECT DETECTION OF DARK MATTER FROM GALAXY CLUSTERS IN FERMI {gamma}-RAY DATA  

SciTech Connect

Using the Fermi Large Area Telescope (LAT) we search for spectral features in {gamma}-rays coming from regions corresponding to the 18 brightest nearby galaxy clusters determined by the magnitude of their signal line-of-sight integrals. We observe a double-peak-like excess over the diffuse power-law background at photon energies of 110 GeV and 130 GeV with a global statistical significance of up to 3.6{sigma}, independently confirming earlier claims of the same excess from the Galactic center. Interpreting this result as a signal of dark matter annihilations to two monochromatic photon channels in galaxy cluster halos, and fixing the annihilation cross-section from the Galactic center data, we determine the annihilation boost factor due to dark matter subhalos from the data. Our results contribute to a discrimination of the dark matter annihilations from astrophysical processes and from systematic detector effects, offering them as possible explanations for the Fermi-LAT excess.

Hektor, A.; Raidal, M.; Tempel, E., E-mail: andi.hektor@cern.ch, E-mail: martti.raidal@cern.ch, E-mail: elmo@aai.ee [National Institute of Chemical Physics and Biophysics, Raevala 10, 10143 Tallinn(Estonia)

2013-01-10T23:59:59.000Z

38

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

Science Conference Proceedings (OSTI)

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.

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

39

BL Lacertae Objects and the Extragalactic Gamma-Ray Background  

E-Print Network (OSTI)

A tight correlation between gamma-ray and radio emission is found for a sample of BL Lacertae (BL Lac) objects detected by Fermi Gamma-ray Space Telescope (Fermi) and the Energetic Gamma-Ray Experiment Telescope (EGRET). The gamma-ray emission of BL Lac objects exhibits strong variability, and the detection rate of gamma-ray BL Lac objects is low, which may be related to the gamma-ray duty cycle of BL Lac objects. We estimate the gamma-ray duty cycle ~ 0.11, for BL Lac objects detected by EGRET and Fermi. Using the empirical relation of gamma-ray emission with radio emission and the estimated gamma-ray duty cycle, we derive the gamma-ray luminosity function (LF) of BL Lac objects from their radio LF. Our derived gamma-ray LF of BL Lac objects can almost reproduce that calculated with the recently released Fermi bright active galactic nuclei (AGN) sample. We find that about 45% of the extragalactic diffuse gamma-ray background (EGRB) is contributed by BL Lac objects. Combining the estimate of the quasar contri...

Li, Fan

2011-01-01T23:59:59.000Z

40

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

SciTech Connect

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.

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

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
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41

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

SciTech Connect

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.

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

42

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

SciTech Connect

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.

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

43

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

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).

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

44

A Gamma-Ray Burst Bibliography, 1973-2001 UC Berkeley Space Sciences Laboratory, Berkeley, CA 94720-7450  

E-Print Network (OSTI)

A Gamma-Ray Burst Bibliography, 1973-2001 K. Hurley UC Berkeley Space Sciences Laboratory, Berkeley, CA 94720-7450 Abstract. On the average, 1.5 new publications on cosmic gamma-ray bursts enter have been tracking the gamma-ray burst literature for about the past twenty-one years, keeping

California at Berkeley, University of

45

Implications of the Fermi-LAT gamma ray observation on minimal $U(1)_{B-L}$ model  

E-Print Network (OSTI)

The recent observation of Fermi-LAT signal of monochromatic gamma ray has drawn much attention. One of the possible explanations for this observation can be due to the annihilation of the dark matter particles into two photons. In our article we adopt a $B-L$ extended Standard Model which contains a singlet scalar and three right-handed neutrinos. The vacuum expectation value of the singlet scalar breaks the $U(1)_{B-L}$ symmetry. We have imposed a $Z_2$ symmetry in such a way that the 3rd generation right-handed neutrino is qualified as the dark matter candidate. This right-handed neutrino, having mass 130 GeV, annihilates into two photons through a resonance channel via a heavy scalar. We constrain the scalar mixing angle, $\\cos\\alpha \\geq 0.986$ by demanding the desired cross-section $\\langle\\sigma v\\rangle_{\\gamma \\gamma}$ for the Fermi-line. We have also checked that this mixing angle allows vacuum stability of this model up to $10^5$ GeV. This might hints that this $U(1)_{B-L}$ extended model that can explain Fermi-LAT signal of monochromatic gamma ray line must be a part of larger symmetry group at some high scale.

Tanushree Basak; Tanmoy Mondal

2013-07-31T23:59:59.000Z

46

Gamma-Ray Bursts from Primordial Quark Objects in Space  

E-Print Network (OSTI)

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.

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

1997-11-28T23:59:59.000Z

47

Fermi LAT Observation of Diffuse Gamma-Rays Produced through Interactions Between Local Interstellar Matter and High Energy Cosmic Rays  

DOE Green Energy (OSTI)

Observations by the Large Area Telescope (LAT) on the Fermi mission of diffuse {gamma}-rays in a mid-latitude region in the third quadrant (Galactic longitude l from 200{sup o} to 260{sup o} and latitude |b| from 22{sup o} to 60{sup o}) are reported. The region contains no known large molecular cloud and most of the atomic hydrogen is within 1 kpc of the solar system. The contributions of {gamma}-ray point sources and inverse Compton scattering are estimated and subtracted. The residual {gamma}-ray intensity exhibits a linear correlation with the atomic gas column density in energy from 100 MeV to 10 GeV. The measured integrated {gamma}-ray emissivity is (1.63 {+-} 0.05) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} and (0.66 {+-} 0.02) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} above 100 MeV and above 300 MeV, respectively, with an additional systematic error of {approx}10%. The differential emissivity from 100 MeV to 10 GeV agrees with calculations based on cosmic ray spectra consistent with those directly measured, at the 10% level. The results obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar system in regions studied are close to the local interstellar spectra inferred from direct measurements at the Earth within {approx}10%.

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.; 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; Burnett, T.H.; /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /Royal Inst. Tech., Stockholm /Stockholm U., OKC /DAPNIA, Saclay /INFN, Perugia /Perugia U. /NASA, Goddard /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stockholm U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /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. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Bari U. /INFN, Bari /INFN, Bari; /more authors..

2012-03-30T23:59:59.000Z

48

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)

-TIME FERMI LARGE AREA TELESCOPE GAMMA-RAY BURST AFTERGLOWS C. A. Swenson1 , A. Maxham2 , P. W. A. Roming1 2010 June 11; published 2010 June 28 ABSTRACT GRB 090926A was detected by both the Gamma-ray Burst the predicted gamma-ray fluence, as would have been seen by the Burst Alert Telescope (BAT) on board Swift

California at Berkeley, University of

49

FERMI LARGE AREA TELESCOPE DETECTION OF BRIGHT {gamma}-RAY OUTBURSTS FROM THE PECULIAR QUASAR 4C +21.35  

SciTech Connect

In this paper, we report on the two-year-long Fermi-Large Area Telescope observation of the peculiar blazar 4C +21.35 (PKS 1222+216). This source was in a quiescent state from the start of the science operations of the Fermi Gamma-ray Space Telescope in 2008 August until 2009 September, and then became more active, with gradually increasing flux and some moderately bright flares. In 2010 April and June, 4C +21.35 underwent a very strong GeV outburst composed of several major flares characterized by rise and decay timescales of the order of a day. During the outburst, the GeV spectra of 4C +21.35 displayed a broken power-law form with spectral breaks observed near 1-3 GeV photon energies. We demonstrate that, at least during the major flares, the jet in 4C +21.35 carried a total kinetic luminosity comparable to the total accretion power available to feed the outflow. We also discuss the origin of the break observed in the flaring spectra of 4C +21.35. We show that, in principle, a model involving annihilation of the GeV photons on the He II Lyman recombination continuum and line emission of 'broad-line region' clouds may account for such. However, we also discuss the additional constraint provided by the detection of 4C +21.35 at 0.07-0.4 TeV energies by the MAGIC telescope, which coincided with one of the GeV flares of the source. We argue that there are reasons to believe that the {approx}< TeV emission of 4C +21.35 (as well as the GeV emission of the source, if co-spatial) is not likely to be produced inside the broad-line region zone of highest ionization ({approx}10{sup 17} cm from the nucleus), but instead originates further away from the active center, namely, around the characteristic scale of the hot dusty torus surrounding the 4C +21.35 nucleus ({approx}10{sup 19} cm).

Tanaka, Y. T.; Stawarz, L.; Saito, S.; Ohno, M.; Takahashi, T. [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Thompson, D. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); D'Ammando, F. [IASF Palermo, 90146 Palermo (Italy); Fegan, S. J. [Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS/IN2P3, Palaiseau (France); Lott, B.; Escande, L. [Universite Bordeaux 1, CNRS/IN2p3, Centre d'Etudes Nucleaires de Bordeaux Gradignan, 33175 Gradignan (France); Wood, D. L.; Finke, J. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Cheung, C. C. [National Research Council Research Associate, National Academy of Sciences, Washington, DC 20001 (United States); Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Donato, D. [Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Chiang, J. [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); Giroletti, M. [INAF Istituto di Radioastronomia, 40129 Bologna (Italy); Schinzel, F. K. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Iafrate, G.; Longo, F., E-mail: tanaka@astro.isas.jaxa.jp [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy)

2011-05-20T23:59:59.000Z

50

Very High Energy Observations of Satellite?Detected Gamma?Ray Bursts  

Science Conference Proceedings (OSTI)

Recent results from the Fermi Gamma?ray Space Telescope indicate that gamma?ray bursts (GRBs) are capable of producing photons with energies up to ?90 GeV in the rest frame of the burst. The Fermi?LAT may not be sensitive to the highest energy photons associated with GRBs and ground?based

Taylor Aune; The Milagro Collaboration; The VERITAS collaboration

2011-01-01T23:59:59.000Z

51

SLAC National Accelerator Laboratory - Fermi Gamma-ray Space...  

NLE Websites -- All DOE Office Websites (Extended Search)

Earth Blocking Charged Particles This illustration shows an example of the Earth's geomagnetic field and the Earth's "shadow" blocking particles of one charge while allowing...

52

SINGLE- AND TWO-COMPONENT GAMMA-RAY BURST SPECTRA IN THE FERMI GBM-LAT ENERGY RANGE  

Science Conference Proceedings (OSTI)

Most Fermi gamma-ray burst spectra appear as either a broken power law extending to GeV energies or as a broken power with a separate GeV power-law component. Here we show that such spectra can be understood in terms of magnetically dominated relativistic jets where a dissipative photosphere produces the prompt MeV emission, which is extended into the GeV range by inverse Compton scattering in the external shock, with possible contributions from a reverse shock as well. The bulk Lorentz factors required in these models are in the range of 300-600, and the MeV-GeV time delays arise naturally. In some cases an optical flash and a sub-dominant thermal component are also present.

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

2012-08-10T23:59:59.000Z

53

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

E-Print Network (OSTI)

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.

Preston Jones

2006-06-23T23:59:59.000Z

54

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

SciTech Connect

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.

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

55

On The {\\it Fermi} -Lat Surplus of the Diffuse Galactic Gamma-Ray Emission  

E-Print Network (OSTI)

Recent observations of the diffuse Galactic \\gr emission (DGE) by the {\\it Fermi} Large Area Telescope ({\\it Fermi}-LAT) have shown significant deviations, above a few GeV until about 100 GeV, from DGE models that use the GALPROP code for the propagation of cosmic ray (CR) particles outside their sources in the Galaxy and their interaction with the target distributions of the interstellar gas and radiation fields. The surplus of radiation observed is most pronounced in the inner Galaxy, where the concentration of CR sources is strongest. The present study investigates this "{\\it Fermi}-LAT Galactic Plane Surplus" by estimating the \\gr emission from the sources themselves, which is disregarded in the above DGE models. It is shown that indeed the expected hard spectrum of CRs, still confined in their sources (SCRs), can explain this surplus. The method is based on earlier studies regarding the so-called EGRET GeV excess which by now is generally interpreted as an instrumental effect. The contribution from SCRs ...

Voelk, Heinrich J

2013-01-01T23:59:59.000Z

56

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

Science Conference Proceedings (OSTI)

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.

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

57

Gamma Ray Bursts  

E-Print Network (OSTI)

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.

Peter Mészáros

2012-04-09T23:59:59.000Z

58

Gamma ray burst delay times probe the geometry of momentum space  

E-Print Network (OSTI)

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.

Laurent Freidel; Lee Smolin

2011-03-29T23:59:59.000Z

59

Gamma-Ray Bursts  

E-Print Network (OSTI)

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.

P. Meszaros

2006-05-09T23:59:59.000Z

60

Gamma Ray Pulsars: Observations  

E-Print Network (OSTI)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-20 GeV range. Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

David J. Thompson

2001-01-03T23:59:59.000Z

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61

VERY RAPID HIGH-AMPLITUDE GAMMA-RAY VARIABILITY IN LUMINOUS BLAZAR PKS 1510-089 STUDIED WITH FERMI-LAT  

SciTech Connect

Here we report on the detailed analysis of the {gamma}-ray light curve of a luminous blazar PKS 1510-089 observed in the GeV range with the Large Area Telescope (LAT) on board the Fermi satellite during the period 2011 September-December. By investigating the properties of the detected three major flares with the shortest possible time binning allowed by the photon statistics, we find a variety of temporal characteristics and variability patterns. This includes a clearly asymmetric profile (with a faster flux rise and a slower decay) of the flare resolved on sub-daily timescales, a superposition of many short uncorrelated flaring events forming the apparently coherent longer-duration outburst, and a huge single isolated outburst unresolved down to the timescale of 3 hr. In the latter case we estimate the corresponding {gamma}-ray flux doubling timescale to be below 1 hr, which is extreme and never previously reported for any active galaxy in the GeV range. The other unique finding is that the total power released during the studied rapid and high-amplitude flares constitutes the bulk of the power radiatively dissipated in the source and a significant fraction of the total kinetic luminosity of the underlying relativistic outflow. Our analysis allows us to access directly the characteristic timescales involved in shaping the energy dissipation processes in the source, and to provide constraints on the location and the structure of the blazar emission zone in PKS 1510-089.

Saito, S.; Stawarz, L.; Takahashi, T. [Institute of Space and Astronautical Science JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Tanaka, Y. T. [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Madejski, G. [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); D'Ammando, F., E-mail: ssaitoh@astro.isas.jaxa.jp [Dip. di Fisica, Universita degli Studi di Perugia and INFN, Via A. Pascoli, I-06123 Perugia (Italy)

2013-03-20T23:59:59.000Z

62

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

SciTech Connect

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.

Kippen, Richard Marc [Los Alamos National Laboratory

2012-08-27T23:59:59.000Z

63

The WISE Gamma-Ray Strip Parametrization: The Nature of the Gamma-Ray Active Galactic Nuclei of Uncertain Type  

SciTech Connect

Despite the large number of discoveries made recently by Fermi, the origins of the so called unidentified {gamma}-ray sources remain unknown. The large number of these sources suggests that among them there could be a population that significantly contributes to the isotropic gamma-ray background and is therefore crucial to understand their nature. The first step toward a complete comprehension of the unidentified {gamma}-ray source population is to identify those that can be associated with blazars, the most numerous class of extragalactic sources in the {gamma}-ray sky. Recently, we discovered that blazars can be recognized and separated from other extragalactic sources using the infrared (IR) WISE satellite colors. The blazar population delineates a remarkable and distinctive region of the IR color-color space, the WISE blazar strip. In particular, the subregion delineated by the {gamma}-ray emitting blazars is even narrower and we named it as the WISE Gamma-ray Strip (WGS). In this paper we parametrize the WGS on the basis of a single parameter s that we then use to determine if {gamma}-ray Active Galactic Nuclei of the uncertain type (AGUs) detected by Fermi are consistent with the WGS and so can be considered blazar candidates. We find that 54 AGUs out of a set 60 analyzed have IR colors consistent with the WGS; only 6 AGUs are outliers. This result implies that a very high percentage (i.e., in this sample about 90%) of the AGUs detected by Fermi are indeed blazar candidates.

Massaro, F.; /SLAC; D'Abrusco, R.; /Harvard-Smithsonian Ctr. Astrophys.; Tosti, G.; /Perugia U. /INFN, Perugia; Ajello, M.; /SLAC; Gasparrini, D.; /ESRIN, Frascati; Grindlay, J.E.; Smith, Howard A.; /Harvard-Smithsonian Ctr. Astrophys.

2012-04-02T23:59:59.000Z

64

A COMPREHENSIVE ANALYSIS OF FERMI GAMMA-RAY BURST DATA. II. E{sub p} EVOLUTION PATTERNS AND IMPLICATIONS FOR THE OBSERVED SPECTRUM-LUMINOSITY RELATIONS  

SciTech Connect

We present a time-resolved spectral analysis of 51 long and 11 short bright gamma-ray bursts (GRBs) observed with the Fermi/Gamma-Ray Burst Monitor, paying special attention to E{sub p} evolution within each burst. Among eight single-pulse long GRBs, five show an evolution from hard to soft, while three show intensity tracking. The multi-pulse long GRBs have more complicated patterns. Statistically, the hard-to-soft evolution pulses tend to be more asymmetric than the intensity-tracking ones, with a steeper rising wing than the falling wing. Short GRBs have E{sub p} tracking intensity exclusively with the 16 ms time-resolution analysis. We performed a simulation analysis and suggest that for at least some bursts, the late intensity-tracking pulses could be a consequence of overlapping hard-to-soft pulses. However, the fact that the intensity-tracking pattern exists in the first pulse of the multi-pulse long GRBs and some single-pulse GRBs, suggests that intensity tracking is an independent component, which may operate in some late pulses as well. For the GRBs with measured redshifts, we present a time-resolved E{sub p} - L{sub {gamma},iso} correlation analysis and show that the scatter of the correlation is comparable to that of the global Amati/Yonetoku relation. We discuss the predictions of various radiation models regarding E{sub p} evolution, as well as the possibility of a precessing jet in GRBs. The data pose a great challenge to each of these models, and hold the key to unveiling the physics behind GRB prompt emission.

Lu Ruijing; Wei Junjie; Liang Enwei; Lue Lianzhong [Department of Physics and GXU-NAOC Center for Astrophysics and Space Sciences, Guangxi University, Nanning 530004 (China); Zhang Binbin [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Lue Houjun; Zhang Bing [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States); Lei Weihua, E-mail: lew@gxu.edu.cn, E-mail: zhang@physics.unlv.edu [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2012-09-10T23:59:59.000Z

65

Gamma Ray Pulsars: Multiwavelength Observations  

E-Print Network (OSTI)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The seven or more pulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. For all the known gamma-ray pulsars, multiwavelength observations and theoretical models based on such observations offer the prospect of gaining a broad understanding of these rotating neutron stars. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2007, will provide a major advance in sensitivity, energy range, and sky coverage.

David J. Thompson

2003-12-10T23:59:59.000Z

66

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

SciTech Connect

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.

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

2012-05-01T23:59:59.000Z

67

Building ISOC Status Displays for the Large AreaTelescope aboard the Gamma Ray Large Area Space Telescope (GLAST) Observatory  

DOE Green Energy (OSTI)

In September 2007 the Gamma Ray Large Area Space Telescope (GLAST) is scheduled to launch aboard a Delta II rocket in order to put two high-energy gamma-ray detectors, the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM) into low earth orbit. The Instrument Science Operations Center (ISOC) at SLAC is responsible for the LAT operations for the duration of the mission, and will therefore build an operations center including a monitoring station at SLAC to inform operations staff and visitors of the status of the LAT instrument and GLAST. This monitoring station is to include sky maps showing the location of GLAST in its orbit as well as the LAT's projected field of view on the sky containing known gamma-ray sources. The display also requires a world map showing the locations of GLAST and three Tracking and Data Relay Satellites (TDRS) relative to the ground, their trail lines, and ''footprint'' circles indicating the range of communications for each satellite. The final display will also include a space view showing the orbiting and pointing information of GLAST and the TDRS satellites. In order to build the displays the astronomy programs Xephem, DS9, SatTrack, and STK were employed to model the position of GLAST and pointing information of the LAT instrument, and the programming utilities Python and Cron were used in Unix to obtain updated information from database and load them into the programs at regular intervals. Through these methods the indicated displays were created and combined to produce a monitoring display for the LAT and GLAST.

Ketchum, Christina; /SLAC

2006-09-01T23:59:59.000Z

68

Status of GLAST, the Gamma-ray Large-area Space Telescope  

SciTech Connect

GLAST is a satellite-based observatory consisting of the Large-Area Telescope (LAT), a modular 4 x 4-tower pair-conversion telescope with a field-of-view greater than 2 steradians, capable of measuring gamma-ray energies in the range 20 MeV to 300 GeV, and the GLAST Burst Monitor (GBM), a set of NaI and BGO detectors covering 8 steradians and sensitive to photons with energies between 10 keV and 25 MeV, allowing for correlative observations of transient events. The observatory is currently being constructed and is scheduled to be launched in August 2007.

Rochester, L.; /SLAC

2005-12-14T23:59:59.000Z

69

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

E-Print Network (OSTI)

-TIME FERMI LARGE AREA TELESCOPE GAMMA-RAY BURST AFTERGLOWS C. A. Swenson1 , A. Maxham2 , P. W. A. Roming1 2010 June 11; published 2010 June 28 ABSTRACT GRB 090926A was detected by both the Gamma-ray Burst the predicted gamma-ray fluence, as would have been seen by the Burst Alert Telescope (BAT) on board Swift

Enomoto, Ryoji

70

Solar Gamma Rays Powered by Secluded Dark Matter  

E-Print Network (OSTI)

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.

Brian Batell; Maxim Pospelov; Adam Ritz; Yanwen Shang

2009-10-08T23:59:59.000Z

71

Solar gamma rays powered by secluded dark matter  

Science Conference Proceedings (OSTI)

Secluded dark matter models, in which weakly interacting massive particles 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.

Batell, Brian; Shang Yanwen [Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2J 2W9 (Canada); Pospelov, Maxim [Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2J 2W9 (Canada); Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 (Canada); Ritz, Adam [Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 (Canada)

2010-04-01T23:59:59.000Z

72

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

E-Print Network (OSTI)

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

Simiæ, Slobodan N.

73

DOE Science Showcase - Gamma-Ray Bursts | OSTI, US Dept of Energy, Office  

Office of Scientific and Technical Information (OSTI)

Gamma-Ray Bursts Gamma-Ray Bursts Fermi Sees Record Gamma-ray Burst, May 3, 2013 Fermi Sees Record Gamma-ray Burst, May 3, 2013Credit: NASA/DOE/Fermi LAT Collection Gamma-ray bursts are short-lived bursts of gamma-ray photons observed in distant galaxies and thought to be triggered by supernovae or exploding stars. Gamma-ray bursts have been an observational and theoretical challenge since they were first observed in the 60s. Department of Energy physicists are participating in international collaborations of scientists to gain a better understanding of how gamma-ray bursts are formed and how they affect our universe. Learn about the science behind gamma-ray bursts In the OSTI Collections: Gamma Ray Bursts by Dr. William Watson, physicist, of OSTI's staff. This latest white paper includes a compilation of

74

In the OSTI Collections: Gamma-Ray Bursts | OSTI, US Dept of Energy, Office  

Office of Scientific and Technical Information (OSTI)

Gamma-Ray Bursts Gamma-Ray Bursts The Fermi Gamma-ray Space Telescope and its first lessons Seeing indirectly by shining light through light Gamma-ray bursters The Large Synoptic Survey Telescope An emerging picture References Research Organizations Instrument Websites Reports Available through OSTI's SciTech Connect Additional Reference The night sky, as our unaided eyes present it to us, obviously contains the sun, the moon, thousands of stars, a few planets, a milky band of light that stretches from horizon to horizon, the occasional meteor or meteor shower, and sometimes a comet. A few centuries of examination with eyes aided by many kinds of instruments have revealed more and more of the nature of these objects-for example, that the planets are more or less like the Earth, orbiting the sun, with some planets having moons of various

75

GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES  

SciTech Connect

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.

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

76

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

E-Print Network (OSTI)

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.

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

2009-01-05T23:59:59.000Z

77

Gamma ray detector shield  

DOE Patents (OSTI)

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.

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

1985-08-26T23:59:59.000Z

78

Gamma-Ray Burst Physics with GLAST  

SciTech Connect

The Gamma-ray Large Area Space Telescope (GLAST) is an international space mission that will study the cosmos in the energy range 10 keV-300 GeV, the upper end of which is one of the last poorly observed region of the celestial electromagnetic spectrum. The ancestor of the GLAST/LAT was the Energetic Gamma Ray Experiment Telescope (EGRET) detector, which flew onboard the Compton Gamma Ray Observatory (CGRO). The amount of information and the step forward that the high energy astrophysics made thanks to its 9 years of observations are impressive. Nevertheless, EGRET uncovered the tip of the iceberg, raising many questions, and it is in the light of EGRET's results that the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope, the Large Area Telescope (LAT) vastly more capable than instruments own previously, as well as a secondary instrument, the GLAST Bursts Monitor, or GBM, to augment the study of gamma-ray bursts. Gamma-Ray Bursts (GRBs) science is one of the most exciting challenges for the GLAST mission, exploring the high energy emission of one of the most intense phenomena in the sky, shading light on various problems: from the acceleration of particles to the emission processes, to more exotic physics like Quantum Gravity effect. In this paper we report the work done so far in the simulation development as well as the study of the LAT sensitivity to GRB.

Omodei, N.; /INFN, Pisa

2006-10-06T23:59:59.000Z

79

Gamma-ray Astronomy  

E-Print Network (OSTI)

The relevance of gamma-ray astronomy to the search for the origin of the galactic and, to a lesser extent, the ultra-high-energy cosmic rays has long been recognised. The current renaissance in the TeV gamma-ray field has resulted in a wealth of new data on galactic and extragalactic particle accelerators, and almost all the new results in this field were presented at the recent International Cosmic Ray Conference (ICRC). Here I summarise the 175 papers submitted on the topic of gamma-ray astronomy to the 30th ICRC in Merida, Mexico in July 2007.

Hinton, Jim

2007-01-01T23:59:59.000Z

80

Gamma-ray Astronomy  

E-Print Network (OSTI)

The relevance of gamma-ray astronomy to the search for the origin of the galactic and, to a lesser extent, the ultra-high-energy cosmic rays has long been recognised. The current renaissance in the TeV gamma-ray field has resulted in a wealth of new data on galactic and extragalactic particle accelerators, and almost all the new results in this field were presented at the recent International Cosmic Ray Conference (ICRC). Here I summarise the 175 papers submitted on the topic of gamma-ray astronomy to the 30th ICRC in Merida, Mexico in July 2007.

Jim Hinton

2007-12-20T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Gamma-ray events thunderclouds  

E-Print Network (OSTI)

Andromeda: A mission to determine the gamma-ray burst distance scale F.A. Harrison, W.R. Cook, T was submitted to the STEDI program, and will also be proposed as a NASA Small Explorer. Keywords: bursts, gamma-rays, small missions 1 SCIENTIFIC OBJECTIVES 1.1 Gamma-ray Bursts Gamma-ray bursts GRBs were discovered

California at Berkeley, University of

82

Gamma-Ray Pulsar Studies with GLAST  

E-Print Network (OSTI)

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.

D. J. Thompson

2007-11-27T23:59:59.000Z

83

Gamma-Ray Pulsar Studies With GLAST  

SciTech Connect

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.

Thompson, D.J.; /NASA, Goddard

2011-11-23T23:59:59.000Z

84

Neutrinos from Gamma Ray Bursts  

E-Print Network (OSTI)

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.

Karl Mannheim

2000-10-18T23:59:59.000Z

85

Gamma-ray albedo of the moon  

E-Print Network (OSTI)

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 4 GeV (600 MeV for the inner part of the Moon disc). Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalisation; this makes it a useful "standard candle" for 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 gamma 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.

Igor V. Moskalenko; Troy A. Porter

2007-05-25T23:59:59.000Z

86

Future Facilities for Gamma-Ray Pulsar Studies  

E-Print Network (OSTI)

Pulsars seen at gamma-ray energies offer insight into particle acceleration to very high energies, along with information about the geometry and interaction processes in the magnetospheres of these rotating neutron stars. During the next decade, a number of new gamma-ray facilities will become available for pulsar studies. This brief review describes the motivation for gamma-ray pulsar studies, the opportunities for such studies, and some specific discussion of the capabilities of the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) for pulsar measurements.

D. J. Thompson

2003-10-17T23:59:59.000Z

87

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

SciTech Connect

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.

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

2013-07-20T23:59:59.000Z

88

Exploring the bizarrerie : research on selective physical processes in gamma-ray bursts.  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs) are the mysterious, short and intense flashes of gamma-rays in the space, and are believed to originate from the rare, explosively devastating,… (more)

Shen, Rongfeng

2010-01-01T23:59:59.000Z

89

Fermi-LAT Observation of Quiescent Solar Emission  

E-Print Network (OSTI)

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope is a pair-conversion detector designed to study the gamma-ray sky in the energy range 30 MeV to 300 GeV. Fermi has detected high-energy gamma rays from the quiet Sun produced by interactions of cosmic-ray nucleons with the solar surface, and cosmic-ray electrons with solar photons in the heliosphere. While the Sun was detected by EGRET on CGRO with low statistics, Fermi provides high-quality detections on a daily basis allowing variability to be addressed. Such observations will provide a probe of the extreme conditions near the solar surface and a monitor the modulation of cosmic rays over the inner heliosphere. We discuss the study of the quiescent solar emission including spectral analysis of its two components, disk and inverse Compton.

Orlando, Elena

2009-01-01T23:59:59.000Z

90

A supersymmetric origin of gamma ray bursts  

E-Print Network (OSTI)

Bright bursts of gamma rays from outer space have been puzzling Astronomers for more than thirty years and there is still no conceptually complete model for the phenomenon within the standard model of particle physics. Is it time to consider a supersymmetric (SUSY) origin for these bursts to add to the astronomical indications of supersymmetry from dark matter?

L. Clavelli

2004-10-01T23:59:59.000Z

91

Gamma Ray Bursts Sudden, intense flashes of gamma rays  

E-Print Network (OSTI)

. Sakamoto1,12 , C. L. Sarazin13 , P. Schady6,10 , M. Stamatikos1,12 & S. E. Woosley14 Gamma-ray bursts (GRBs. Identification of two classes of gamma-ray bursts. Astrophys. J. 413, L101­L104 (1993). 2. Fruchter, A. et al). 3. Woosley, S. E. Gamma-ray bursts from stellar mass accretion disks around black holes. Astrophys

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

92

Search for Spatially Extended Fermi-LAT Sources Using Two Years of Data  

SciTech Connect

Spatial extension is an important characteristic for correctly associating {gamma}-ray-emitting sources with their counterparts at other wavelengths and for obtaining an unbiased model of their spectra. We present a new method for quantifying the spatial extension of sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi). We perform a series of Monte Carlo simulations to validate this tool and calculate the LAT threshold for detecting the spatial extension of sources. We then test all sources in the second Fermi -LAT catalog (2FGL) for extension. We report the detection of seven new spatially extended sources.

Lande, Joshua; Ackermann, Markus; Allafort, Alice; Ballet, Jean; Bechtol, Keith; Burnett, Toby; Cohen-Tanugi, Johann; Drlica-Wagner, Alex; Funk, Stefan; Giordano, Francesco; Grondin, Marie-Helene; Kerr, Matthew; Lemoine-Goumard, Marianne

2012-07-13T23:59:59.000Z

93

Gamma-ray burst populations.  

E-Print Network (OSTI)

??Over the last fifty years the field of gamma-ray bursts has shown incredible growth, but the amassing of data has also left observers and theorists… (more)

Virgili, Francisco J.

2011-01-01T23:59:59.000Z

94

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

Science Conference Proceedings (OSTI)

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.

Massaro, Francesco

2012-08-03T23:59:59.000Z

95

Explaining the light curves of Gamma-ray Bursts with precessing jets  

E-Print Network (OSTI)

A phenomenological model is presented to explain the light curves of gamma-ray bursts. Gamma-rays are produced in a narrow beam which sweeps through space due to the precession of a slaved accretion disc. The light curve expected from such a precessing luminosity cone can explain the complex temporal behavior of bright gamma-ray bursts.

Simon Portegies Zwart

1999-03-13T23:59:59.000Z

96

The effect of flight line spacing on radioactivity inventory and spatial feature characteristics of airborne gamma-ray spectrometry data  

Science Conference Proceedings (OSTI)

Airborne Gamma Spectrometry (AGS) is well suited to the mapping of radioactivity in the environment. Flight parameters (e.g. speed and line spacing) directly affect the rate of area coverage, cost, and data quality of any survey. The influences of line ...

D. C. W. Sanderson; A. J. Cresswell; D. C. White

2008-01-01T23:59:59.000Z

97

Perspectives on Gamma-Ray Pulsar Emission  

SciTech Connect

Pulsars are powerful sources of radiation across the electromagnetic spectrum. This paper highlights some theoretical insights into non-thermal, magnetospheric pulsar gamma-ray radiation. These advances have been driven by NASA's Fermi mission, launched in mid-2008. The Large Area Telescope (LAT) instrument on Fermi has afforded the discrimination between polar cap and slot gap/outer gap acceleration zones in young and middle-aged pulsars. Altitude discernment using the highest energy pulsar photons will be addressed, as will spectroscopic interpretation of the primary radiation mechanism in the LAT band, connecting to both polar cap/slot gap and outer gap scenarios. Focuses will mostly be on curvature radiation and magnetic pair creation, including population trends that may afford probes of the magnetospheric accelerating potential.

Baring, Matthew G. [Department of Physics and Astronomy, MS-108, Rice University, P. O. Box 1892, Houston, TX 77251-1892 (United States)

2011-09-21T23:59:59.000Z

98

FERMI LARGE AREA TELESCOPE OBSERVATION OF SUPERNOVA REMNANT S147  

Science Conference Proceedings (OSTI)

We present an analysis of gamma-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope in the region around supernova remnant (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) Multiplication-Sign 10{sup -8} photons cm{sup -2} s{sup -1}, corresponding to a luminosity of 1.3 Multiplication-Sign 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 the prominent H{alpha} filaments of SNR 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. The reacceleration of the pre-existing cosmic rays and subsequent adiabatic compression in the filaments is sufficient to provide the energy density required of high-energy protons.

Katsuta, J.; Uchiyama, Y.; Tanaka, T.; Tajima, H.; Bechtol, K.; Funk, S.; Lande, J. [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); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Hanabata, Y. [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Lemoine-Goumard, M. [Universite Bordeaux 1, CNRS/IN2p3, Centre d'Etudes Nucleaires de Bordeaux Gradignan, 33175 Gradignan (France); Takahashi, T., E-mail: katsuta@slac.stanford.edu, E-mail: uchiyama@slac.stanford.edu [Institute of Space and Astronautical Science, Japanese Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2012-06-20T23:59:59.000Z

99

The Ptolemaic Gamma-Ray Burst Universe  

E-Print Network (OSTI)

The BATSE experiment on GRO has demonstrated the isotropic arrival directions and flat log N vs. log S of cosmic gamma-ray bursts. These data are best explained if the burst sources are distributed throughout an extended spherical Galactic halo, as previously suggested by Jennings. The halo’s radius is at least 40 Kpc, and probably is more than 100 Kpc. I consider possible origins of this halo, including primordial formation and neutron stars recoiling from their birthplaces in the Galactic disc. A simple geometrical model leads to a predicted relation between the dipole and quadrupole anisotropy. I suggest that neutron stars born with low recoil become millisecond pulsars, while those born with high recoil become the sources of gamma-ray bursts; these populations are nearly disjoint. Quiescent counterparts of gamma-ray bursts are predicted to be undetectably faint. 2 The first results from the BATSE on GRO (BATSE Science Team 1991) have revived the question of the distribution of gamma-ray burst sources in space. Their chief results, isotropy of gamma-ray burst directions and a log N vs. log S slope significantly flatter than-1.5, confirm earlier reports (see, for example, Meegan, Fishman and Wilson 1985 and the review by Cline 1984). Questions of relative calibration of different instruments and the paucity of good directional data permitted skepticism in the past. Such skepticism is no longer tenable, and the theoretical questions raised earlier must be faced. An isotropic distribution of sources implies that, out to the maximum distance of observation permitted by instrumental sensitivity, all directions contain equivalent source populations. The source population for an observed flux or fluence S is expressed as the integral N ( ˆ ? ?, S) =

J. I. Katz

1992-01-01T23:59:59.000Z

100

Real time gamma-ray signature identifier  

DOE Patents (OSTI)

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.

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

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Temporal Deconvolution study of Long and Short Gamma-Ray Burst Light curves  

E-Print Network (OSTI)

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.

P. N. Bhat; Michael S. Briggs; Valerie Connaughton; Chryssa Kouveliotou; Alexander J. van der Horst; William Paciesas; Charles A. Meegan; Elisabetta Bissaldi; Michael Burgess; Vandiver Chaplin; Roland Diehl; Gerald Fishman; Gerard Fitzpatrick; Suzanne Foley; Melissa Gibby; Misty M. Giles; Adam Goldstein; Jochen Greiner; David Gruber; Sylvain Guiriec; Andreas von Kienlin; Marc Kippen; Sheila McBreen; Robert Preece; Arne Rau; Dave Tierney; Colleen Wilson-Hodge

2011-09-19T23:59:59.000Z

102

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

SciTech Connect

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.

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

103

Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant  

Science Conference Proceedings (OSTI)

We present an analysis of the gamma-ray measurements by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is {approx} 1 x 10{sup 33} erg s{sup -1} between 1-100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0{sup o}.7 {+-} 0{sup o}.1 and 1{sup o}.6 {+-} 0{sup o}.1. Given the association among X-ray rims, H{alpha} filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

Katagiri, H.; /Ibaraki U., Mito; Tibaldo, L.; /INFN, Padua /Padua U. /Paris U., VI-VII; Ballet, J.; /Paris U., VI-VII; Giordano, F.; /Bari U. /Bari Polytechnic /INFN, Bari; Grenier, I.A.; /Paris U., VI-VII; Porter, T.A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Roth, M.; /Washington U., Seattle; Tibolla, O.; /Wurzburg U.; Uchiyama, Y.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Yamazaki, R.; /Sagamihara, Aoyama Gakuin U.

2011-11-08T23:59:59.000Z

104

Gamma-Ray Burst Lines  

E-Print Network (OSTI)

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.

Michael S. Briggs

1999-10-20T23:59:59.000Z

105

Modeling gamma-ray bursts.  

E-Print Network (OSTI)

??Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground… (more)

Maxham, Amanda

2011-01-01T23:59:59.000Z

106

The Gamma-ray Albedo of the Moon  

E-Print Network (OSTI)

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 normalisation; 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.

Igor V. Moskalenko; Troy A. Porter

2007-08-21T23:59:59.000Z

107

Gamma Ray Bursts and CETI  

E-Print Network (OSTI)

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.

Frank D. Smith Jr

1993-02-10T23:59:59.000Z

108

CdZnTe technology for gamma ray detectors  

Science Conference Proceedings (OSTI)

CdZnTe detector technology has been developed at NASA Goddard for imaging and spectroscopy applications in hard x-ray and gamma ray astronomy. A CdZnTe strip detector array with capabilities for arc second imaging and spectroscopy has been built as a prototype for a space flight gamma ray burst instrument. CdZnTe detectors also have applications for medical imaging

Carl Stahle; Jack Shi; Peter Shu; Scott Barthelmy; Ann Parsons; Steve Snodgrass

1998-01-01T23:59:59.000Z

109

Gamma ray bursts ROBERT S MACKAY  

E-Print Network (OSTI)

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

Rourke, Colin

110

Fermi Large Area Telescope Operations: Progress Over 4 Years  

SciTech Connect

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.

Cameron, Robert A.; /SLAC

2012-06-28T23:59:59.000Z

111

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

E-Print Network (OSTI)

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 Bursts Apparently high gamma-ray efficiency. Highly magnetized flow? Roming et al., 2005 #12;Surprises

California at Santa Cruz, University of

112

LIGHT CURVES OF SWIFT GAMMA RAY BURSTS  

E-Print Network (OSTI)

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. Subject headings: gamma-rays: bursts 1.

Paolo Cea

2006-01-01T23:59:59.000Z

113

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

E-Print Network (OSTI)

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.

B. B. Jones

2002-02-04T23:59:59.000Z

114

SLAC National Accelerator Laboratory - Fermi Sees Record Gamma...  

NLE Websites -- All DOE Office Websites (Extended Search)

Fermi Sees Record Gamma-ray Burst May 3, 2013 A record-setting blast of gamma rays from a dying star in a distant galaxy has wowed astronomers around the world. The eruption, which...

115

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

E-Print Network (OSTI)

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.

A. V. Kuznetsov

2001-11-01T23:59:59.000Z

116

Neutrinos from Gamma Ray Bursts  

E-Print Network (OSTI)

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.

F. Halzen; G. Jaczko

1996-02-07T23:59:59.000Z

117

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

E-Print Network (OSTI)

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.

Katsuaki Asano

2005-03-11T23:59:59.000Z

118

Gamma Ray Burst Neutrinos Probing Quantum Gravity  

E-Print Network (OSTI)

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.

M. C. Gonzalez-Garcia; F. Halzen

2006-11-28T23:59:59.000Z

119

Gamma ray astrophysics: the EGRET results  

E-Print Network (OSTI)

Cosmic gamma rays provide insight into some of the most dynamic processes in the Universe. At the dawn of a new generation of gamma-ray telescopes, this review summarizes results from the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory, the principal predecessor mission studying high-energy photons in the 100 MeV energy range. EGRET viewed a gamma-ray sky dominated by prominent emission from the Milky Way, but featuring an array of other sources, including quasars, pulsars, gamma-ray bursts, and many sources that remain unidentified. A central feature of the EGRET results was the high degree of variability seen in many gamma-ray sources, indicative of the powerful forces at work in objects visible to gamma-ray telescopes.

D J Thompson

2008-11-05T23:59:59.000Z

120

Light Curves of Swift Gamma Ray Bursts  

E-Print Network (OSTI)

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.

Paolo Cea

2006-06-05T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Stellar Sources of Gamma-ray Bursts  

E-Print Network (OSTI)

Correlation analysis of Swift gamma-ray burst coordinates and nearby star locations (catalog Gliese) reveals 4 coincidences with good angular accuracy. The random probability is 4\\times 10^{-5}, so evidencing that coincident stars are indeed gamma-ray burst sources. Some additional search of stellar gamma-ray bursts is discussed.

Luchkov, B I

2011-01-01T23:59:59.000Z

122

Multifrequency Observations of Gamma-Ray Burst  

E-Print Network (OSTI)

Neither a flaring nor a quiescent counterpart to a gamma-ray burst has yet been convincingly identified at any wavelength region. The present status of the search for counterparts of classical gamma-ray bursts is given. Particular emphasis is put on the search for flaring counterparts, i.e. emission during or shortly after the gamma-ray emission.

J. Greiner

1995-10-04T23:59:59.000Z

123

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)

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

Zhang, Bing

124

The Diverse Environments of Gamma-Ray Bursts  

E-Print Network (OSTI)

of a Very Bright Gamma- Ray Burst in a Galactic Halo 3.1Galaxies of Dark Gamma-Ray Bursts: Observational Constraints1.3 Gamma-Ray Burst Classi?cation . . . . . . 1.4 Gamma-Ray

Perley, Daniel Alan

2011-01-01T23:59:59.000Z

125

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

SciTech Connect

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.

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

126

Can precessing jets explain the light curves of Gamma-ray Bursts?  

E-Print Network (OSTI)

We present a phenomenological model to explain the light curves of gamma-ray bursts. In the model a black hole is orbited by a precessing accretion disc which is fed by a neutron star. Gamma-rays are produced in a highly collimated beam via the Blandford-Znajek mechanism. The gamma-ray beam sweeps through space due to the precession of the slaved accretion disc. The light curve expected from such a precessing luminosity cone can explain the complex temporal behavior of observed bright gamma-ray bursts.

Simon Portegies Zwart; Chang-Hwan Lee; Hyun Kyu Lee

1998-08-19T23:59:59.000Z

127

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

Science Conference Proceedings (OSTI)

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.

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

128

THE STRUCTURE AND EMISSION MODEL OF THE RELATIVISTIC JET IN THE QUASAR 3C 279 INFERRED FROM RADIO TO HIGH-ENERGY {gamma}-RAY OBSERVATIONS IN 2008-2010  

SciTech Connect

We present time-resolved broadband observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported {gamma}-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears to be delayed with respect to the {gamma}-ray emission by about 10 days. X-ray observations reveal a pair of 'isolated' flares separated by {approx}90 days, with only weak {gamma}-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the {gamma}-ray flare, while the peak appears in the millimeter (mm)/submillimeter (sub-mm) band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broadband spectra during the {gamma}-ray flaring event by a shift of its location from {approx}1 pc to {approx}4 pc from the central black hole. On the other hand, if the {gamma}-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.

Hayashida, M.; Madejski, G. M.; Chiang, J.; Blandford, R. D.; Buehler, R. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025 (United States); Nalewajko, K. [University of Colorado, UCB 440, Boulder, CO 80309 (United States); Sikora, M. [Nicolaus Copernicus Astronomical Center, 00-716 Warsaw (Poland); Wehrle, A. E. [Space Science Institute, Boulder, CO 80301 (United States); Ogle, P. [Infrared Processing and Analysis Center, California Institute of Technology Pasadena, CA 91125 (United States); Collmar, W. [Max-Planck Institut fuer Extraterrestrische Physik, 85748 Garching (Germany); Larsson, S. [Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Fukazawa, Y.; Itoh, R. [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Stawarz, L. [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Richards, J. L.; Max-Moerbeck, W.; Readhead, A. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Cavazzuti, E.; Ciprini, S. [Agenzia Spaziale Italiana (ASI) Science Data Center, I-00044 Frascati (Roma) (Italy); Gehrels, N., E-mail: mahaya@slac.stanford.edu, E-mail: madejski@slac.stanford.edu, E-mail: knalew@Colorado.edu, E-mail: sikora@camk.edu.pl [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); and others

2012-08-01T23:59:59.000Z

129

A Theory of Gamma-Ray Bursts  

E-Print Network (OSTI)

We present a specific scenario for the link between GRB and hypernovae, based on Blandford-Znajek extraction of black-hole spin energy. Such a mechanism requires a high angular momentum in the progenitor object. The observed association of gamma-ray bursts with type Ibc supernovae leads us to consider massive helium stars that form black holes at the end of their lives as progenitors. We combine the numerical work of MacFadyen & Woosley with analytic calculations, to show that about 1E53 erg each are available to drive the fast GRB ejecta and the supernova. The GRB ejecta are driven by the power output through the open field lines, whereas the supernova is powered by closed filed lines and jet shocks. We also present a much simplified approximate derivation of these energetics. Helium stars that leave massive black-hole remnants in special ways, namely via soft X-ray transients or very massive WNL stars. Since binaries naturally have high angular momentum, we propose a link between black-hole transients and gamma-ray bursts. Recent observations of one such transient, GRO J1655-40/Nova Scorpii 1994, explicitly support this connection: its high space velocity indicates that substantial mass was ejected in the formation of the black hole, and the overabundance of alpha-nuclei, especially sulphur, indicates that the explosion energy was extreme, as in SN 1998bw/GRB 980425. (abstract shortened)

G. E. Brown; C. -H. Lee; R. A. M. J. Wijers; H. K. Lee; G. Israelian; H. A. Bethe

2000-03-23T23:59:59.000Z

130

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

Science Conference Proceedings (OSTI)

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.

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

131

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

E-Print Network (OSTI)

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.

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

2013-03-26T23:59:59.000Z

132

Gamma Ray Burst Central Engines  

E-Print Network (OSTI)

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.

Todd A. Thompson

2008-07-04T23:59:59.000Z

133

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)

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.

Konstantin G. Zloshchastiev

2009-11-30T23:59:59.000Z

134

Black Stars and Gamma Ray Bursts  

E-Print Network (OSTI)

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.

Tanmay Vachaspati

2007-06-08T23:59:59.000Z

135

Gamma ray burst outflows and afterglows.  

E-Print Network (OSTI)

?? We carry out a theoretical investigation of jet propagation in Gamma Ray Bursts and examine the jitter radiation mechanism as a means of producing… (more)

Morsony, Brian J.

2009-01-01T23:59:59.000Z

136

Search for gamma ray burst counterparts  

Science Conference Proceedings (OSTI)

The confident detection of a Gamma Ray Burst counterpart would likely provide the much needed breakthrough in our understanding of the cause and site of bursts. As such

Bradley E. Schaefer

1994-01-01T23:59:59.000Z

137

GeV Emission from Collisional Magnetized Gamma Ray Bursts  

E-Print Network (OSTI)

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.

P. Mészáros; M. J. Rees

2011-04-26T23:59:59.000Z

138

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

E-Print Network (OSTI)

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.

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

2012-05-31T23:59:59.000Z

139

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

E-Print Network (OSTI)

The short gamma-ray burst ­ SGR giant flare connection Kevin Hurley University of California cosmic gamma-ray bursts. There are at least two general ways to approach this problem. One is statistical short gamma-ray bursts (GRBs) could actually be extragalactic giant magnetar flares is not new by any

Enomoto, Ryoji

140

Gamma-Ray Lines from Radiative Dark Matter Decay  

E-Print Network (OSTI)

The decay of dark matter particles which are coupled predominantly to charged leptons has been proposed as a possible origin of excess high-energy positrons and electrons observed by cosmic-ray telescopes PAMELA and Fermi LAT. Even though the dark matter itself is electrically neutral, the tree-level decay of dark matter into charged lepton pairs will generically induce radiative two-body decays of dark matter at the quantum level. Using an effective theory of leptophilic dark matter decay, we calculate the rates of radiative two-body decays for scalar and fermionic dark matter particles. Due to the absence of astrophysical sources of monochromatic gamma rays, the observation of a line in the diffuse gamma-ray spectrum would constitute a strong indication of a particle physics origin of these photons. We estimate the intensity of the gamma-ray line that may be present in the energy range of a few TeV if the dark matter decay interpretation of the leptonic cosmic-ray anomalies is correct and comment on observational prospects of present and future Imaging Cherenkov Telescopes, in particular the CTA.

Mathias Garny; Alejandro Ibarra; David Tran; Christoph Weniger

2010-11-16T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Gamma-Ray Pulsar Visibility  

E-Print Network (OSTI)

PSR J0437-4715 is a millisecond pulsar (MSP) thought to be ``pair formation starved'' (having limited pair cascades due to magnetic photon absorption). Fortunately the general relativistic (GR) electrodynamical model under consideration applicable to this pulsar have few free parameters. We model PSR J0437-4715's visibility, using a 3D model which incorporates the variation of the GR E-field over the polar cap (PC), taking different observer and inclination angles into account. Using this pulsar as a case study, one may generalize to conducting a pulsar population visibility study. We lastly comment on the role of the proposed South African SKA (Square Kilometre Array) prototype, KAT (Karoo Array Telescope), for GLAST gamma-ray pulsar identification.

Venter, C

2005-01-01T23:59:59.000Z

142

Gamma-Ray Pulsar Visibility  

E-Print Network (OSTI)

PSR J0437-4715 is a millisecond pulsar (MSP) thought to be ``pair formation starved'' (having limited pair cascades due to magnetic photon absorption). Fortunately the general relativistic (GR) electrodynamical model under consideration applicable to this pulsar have few free parameters. We model PSR J0437-4715's visibility, using a 3D model which incorporates the variation of the GR E-field over the polar cap (PC), taking different observer and inclination angles into account. Using this pulsar as a case study, one may generalize to conducting a pulsar population visibility study. We lastly comment on the role of the proposed South African SKA (Square Kilometre Array) prototype, KAT (Karoo Array Telescope), for GLAST gamma-ray pulsar identification.

C. Venter; O. C. de Jager; A. Tiplady

2005-10-14T23:59:59.000Z

143

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

E-Print Network (OSTI)

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

California at Santa Cruz, University of

144

A giant radio flare from Cygnus X-3 with associated Gamma-ray emission  

E-Print Network (OSTI)

With frequent flaring activity of its relativistic jets, Cygnus X-3 is one of the most active microquasars and is the only Galactic black hole candidate with confirmed high energy Gamma-ray emission, thanks to detections by Fermi/LAT and AGILE. In 2011, Cygnus X-3 was observed to transit to a soft X-ray state, which is known to be associated with high-energy Gamma-ray emission. We present the results of a multi-wavelength campaign covering a quenched state, when radio emission from Cygnus X-3 is at its weakest and the X-ray spectrum is very soft. A giant (~ 20 Jy) optically thin radio flare marks the end of the quenched state, accompanied by rising non-thermal hard X-rays. Fermi/LAT observations (E >100 MeV) reveal renewed Gamma-ray activity associated with this giant radio flare, suggesting a common origin for all non-thermal components. In addition, current observations unambiguously show that the Gamma-ray emission is not exclusively related to the rare giant radio flares. A 3-week period of Gamma-ray emis...

Corbel, S; Tomsick, J A; Szostek, A; Corbet, R H D; Miller-Jones, J C A; Richards, J L; Pooley, G; Trushkin, S; Dubois, R; Hill, A B; Kerr, M; Max-Moerbeck, W; Readhead, A C S; Bodaghee, A; Tudose, V; Parent, D; Wilms, J; Pottschmidt, K

2012-01-01T23:59:59.000Z

145

Observations of Gamma-Ray Bursts at Extreme Energies  

E-Print Network (OSTI)

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

Aune, Taylor

2012-01-01T23:59:59.000Z

146

Coordinate-Space Hartree-Fock-Bogoliubov Solvers for Super fluid Fermi  

NLE Websites -- All DOE Office Websites (Extended Search)

Coordinate-Space Hartree-Fock-Bogoliubov Solvers for Super fluid Fermi Coordinate-Space Hartree-Fock-Bogoliubov Solvers for Super fluid Fermi Systems in Large Boxes Submitted by mkaczmar on March 29, 2013 - 12:53 Authors: Pei, J.C., Fann, G.I., Harrison, R.J., Nazarewicz, W., Hill, J., Galindo, D., Jia, J. The self-consistent Hartree-Fock-Bogoliubov problem in large boxes can be solved accurately in the coordinate space with the recently developed solvers HFB-AX (2D) and MADNESS-HFB (3D). This is essential for the description of superfluid Fermi systems with complicated topologies and significant spatial extend, such as fissioning nuclei, weakly-bound nuclei, nuclear matter in the neutron star rust, and ultracold Fermi atoms in elongated traps. The HFB-AX solver based on B-spline techniques uses a hybrid MPI and OpenMP programming model for parallel computation for

147

Fermi Large Area Telescope Observations of the Cosmic-Ray Induced  

SciTech Connect

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.

Abdo, A.

2012-02-29T23:59:59.000Z

148

Gamma-Ray Bursts and Particle Astrophysics  

E-Print Network (OSTI)

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.

B. Gendre

2008-07-24T23:59:59.000Z

149

Energetics of Gamma Ray Bursts  

E-Print Network (OSTI)

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.

Raul Jimenez; David Band; Tsvi Piran

2001-03-16T23:59:59.000Z

150

Mining Gamma-Ray Burst Data  

E-Print Network (OSTI)

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/).

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

2000-11-30T23:59:59.000Z

151

Gravitational waves and gamma-ray bursts  

E-Print Network (OSTI)

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.

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

2012-04-18T23:59:59.000Z

152

Diffuse gamma-rays from galactic halos  

E-Print Network (OSTI)

Here we review our current knowledge on diffuse gamma-rays from galactic halos. Estimates of the relative contribution of the various emission processes at low and high latitudes are compared to the data over 6 decades in energy. The observed spectral shape differs from what was expected, especially at ver low and very high energies. In the latter case, above 1 GeV, the sky emission related to gas exceeds the expected pi^0 decay spectrum. At energies below 1 MeV the relatively high gamma-ray intensity indicates at high density of nearly relativistic electrons which would have a strong influence on the energy and ionisation balance of the interstellar medium. Given the EGRET results for the Magellanic Clouds the gamma-ray emissivity in the outer halo is probably small, so that a substantial amount of baryonic dark matter may be hidden at 20-50 kpc radius without inducing observable gamma-ray emission.

M. Pohl

1996-03-12T23:59:59.000Z

153

Current Topics in Gamma-Ray Astrophysics  

Science Conference Proceedings (OSTI)

... into e+–e– pairs ends up as rays. Figure 1 shows a calculation of -ray burst luminosity as ... The integrated energy in gamma-rays from the calculated ...

2000-03-14T23:59:59.000Z

154

Gravitational waves and short gamma ray bursts.  

E-Print Network (OSTI)

??Short hard gamma-ray bursts (GRB) are believed to be produced by compact binary coalescences (CBC) { either double neutron stars or neutron star{black hole binaries.… (more)

Predoi, Valeriu

2012-01-01T23:59:59.000Z

155

Studying Gamma Ray Bursts from a  

E-Print Network (OSTI)

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

Â?umer, Slobodan

156

Can gamma-ray bursts constrain quintessence?  

E-Print Network (OSTI)

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.

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

2005-04-27T23:59:59.000Z

157

Gamma Ray Bursts from Ordinary Cosmic Strings  

E-Print Network (OSTI)

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.

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

1993-02-12T23:59:59.000Z

158

Theoretical Models of Gamma-Ray Bursts  

E-Print Network (OSTI)

Models of gamma ray bursts are reviewed in the light of recent observations of afterglows which point towards a cosmological origin. The physics of fireball shock models is discussed, with attention to the type of light histories and spectra during the gamma-ray phase. The evolution of the remnants and their afterglows is considered, as well as their implications for our current understanding of the mechanisms giving rise to the bursts.

P. Meszaros

1997-11-28T23:59:59.000Z

159

Unidentified Gamma-Ray Sources and Microquasars  

E-Print Network (OSTI)

Some phenomenological properties of the unidentified EGRET detections suggest that there are two distinct groups of galactic gamma-ray sources that might be associated with compact objects endowed with relativistic jets. We discuss different models for gamma-ray production in both microquasars with low- and high-mass stellar companions. We conclude that the parent population of low-latitude and halo variable sources might be formed by yet undetected microquasars and microblazars.

G. E. Romero; I. A Grenier; M. M. Kaufman Bernado; I. F. Mirabel; D. F. Torres

2004-02-12T23:59:59.000Z

160

Results from the Milagro Gamma-Ray Observatory  

E-Print Network (OSTI)

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

California at Santa Cruz, University of

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Fireball/Blastwave Model and Soft Gamma-ray Repeaters  

E-Print Network (OSTI)

Soft gamma-ray repeaters are at determined distances and their positions are known accurately. If observed, afterglows from their soft gamma-ray bursts will provide important clues to the study of the so called "classical gamma-ray bursts". On applying the popular fireball/blastwave model of classical gamma-ray bursts to soft gamma-ray repeaters, it is found that their X-ray and optical afterglows are detectable. Monitoring of the three repeaters is solicited.

Y. F. Huang; Z. G. Dai; T. Lu

1998-10-28T23:59:59.000Z

162

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

SciTech Connect

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.

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

163

Dark matter and pulsar signals for Fermi LAT, PAMELA, ATIC, HESS and WMAP data  

E-Print Network (OSTI)

We analyze new diffuse gamma-ray data from the Fermi Gamma-ray Space Telescope, which do not confirm an excess in the EGRET data at galactic mid-latitudes, in combination with measurements of electron and positron fuxes from PAMELA, Fermi and HESS within the context of three possible sources: dark matter (DM) annihilation or decay into charged leptons, and a continuum distribution of pulsars. We allow for variations in the backgrounds, consider several DM halo profiles, and account for systematic uncertainties in data where possible. We find that all three scenarios represent the data well. The pulsar description holds for a wide range of injection energy spectra. We compare with ATIC data and the WMAP haze where appropriate, but do not fit these data since the former are discrepant with Fermi data and the latter are subject to large systematic uncertainties. We show that for cusped halo profiles, Fermi could observe a spectacular gamma-ray signal of DM annihilation from the galactic center while seeing no excess at mid-latitudes.

V. Barger; Y. Gao; W. -Y. Keung; D. Marfatia; G. Shaughnessy

2009-04-14T23:59:59.000Z

164

The Diffuse Galactic Gamma-Ray Emission Model for GLAST LAT  

E-Print Network (OSTI)

Diffuse emission from the Milky Way dominates the gamma-ray sky. About 80% of the high-energy luminosity of the Milky Way comes from processes in the interstellar medium. The Galactic diffuse emission traces interactions of energetic particles, primarily protons and electrons, with the interstellar gas and radiation field, thus delivering information about cosmic-ray spectra and interstellar mass in distant locations. Additionally, the Galactic diffuse emission is the celestial foreground for the study of gamma-ray point sources and the extragalactic diffuse gamma-ray emission. We will report on the latest developments in the modelling of the Galactic diffuse emission, which will be used for the Gamma Ray Large Area Space Telescope (GLAST) investigations.

Porter, T A; Grenier, I A; Moskalenko, I V; Strong, A W

2007-01-01T23:59:59.000Z

165

The Diffuse Galactic Gamma-Ray Emission Model for GLAST LAT  

Science Conference Proceedings (OSTI)

Diffuse emission from the Milky Way dominates the gamma-ray sky. About 80% of the high-energy luminosity of the Milky Way comes from processes in the interstellar medium. The Galactic diffuse emission traces interactions of energetic particles, primarily protons and electrons, with the interstellar gas and radiation field, thus delivering information about cosmic-ray spectra and interstellar mass in distant locations. Additionally, the Galactic diffuse emission is the celestial foreground for the study of gamma-ray point sources and the extragalactic diffuse gamma-ray emission. We will report on the latest developments in the modeling of the Galactic diffuse emission, which will be used for the Gamma Ray Large Area Space Telescope (GLAST) investigations.

Porter, T.A.; /UC, Santa Cruz; Digel, S.W.; /SLAC /KIPAC, Menlo Park; Grenier, I.A.; /Saclay; Moskalenko, I.V.; /Stanford U., HEPL /KIPAC, Menlo Park; Strong, A.W.; /Garching, Max Planck Inst., MPE

2007-06-13T23:59:59.000Z

166

Gamma ray astrophysics, the extragalactic background light, and new physics  

Science Conference Proceedings (OSTI)

Very high energy gamma-rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. However, recent observations of cosmologically distant emitters by ground based gamma-ray telescopes might be indicative of a higher-than-expected degree of transparency of the universe. One mechanism to explain this observation is the oscillation between photons and axion-like-particles (ALPs). Here we explore this possibility, focusing on photon-ALP conversion in the magnetic fields in and round gamma-ray sources and in the magnetic field of the Milky Way, where some fraction of the ALP flux is converted back into photons. We show that this mechanism can be efficient in allowed regions of the ALP parameter space, as well as in typical configurations of the Galactic Magnetic Field. As case example, we consider the spectrum observed from a HESS source. We also discuss features of this scenario which could be used to distinguish it from standard or other exotic models.

Serpico, Pasquale D.; /Fermilab

2008-09-01T23:59:59.000Z

167

ARE T TAURI STARS GAMMA-RAY EMITTERS?  

Science Conference Proceedings (OSTI)

T Tauri stars are young, low-mass, pre-main-sequence stars surrounded by an accretion disk. These objects present strong magnetic activity and powerful magnetic reconnection events. Strong shocks are likely associated with fast reconnection in the stellar magnetosphere. Such shocks can accelerate particles up to relativistic energies. We aim at developing a simple model to calculate the radiation produced by non-thermal relativistic particles in the environment of T Tauri stars. We want to establish whether this emission is detectable at high energies with the available or forthcoming {gamma}-ray telescopes. We assume that particles (protons and electrons) pre-accelerated in reconnection events are accelerated at shocks through the Fermi mechanism and we study the high-energy emission produced by the dominant radiative processes. We calculate the spectral energy distribution of T Tauri stars up to high energies and we compare the integrated flux obtained with that from a specific Fermi source, 1FGL J1625.8-2429c, that we tentatively associate with this kind of young stellar object. We suggest that under reasonable general conditions nearby T Tauri stars might be detected at high energies and be responsible for some unidentified Fermi sources on the Galactic plane.

Victoria del Valle, Maria; Romero, Gustavo E. [Instituto Argentino de Radioastronomia (IAR), CCT La Plata (CONICET), C.C.5, 1894 Villa Elisa, Buenos Aires (Argentina); Luque-Escamilla, Pedro Luis [Departamento de Ingenieria Mecanica y Minera, Escuela Politecnica Superior de Jaen, Universidad de Jaen, Campus Las Lagunillas s/n, A3, 23071 Jaen (Spain); Marti, Josep; Sanchez-Sutil, Juan Ramon [Departamento de Fisica, Escuela Politecnica Superior de Jaen, Universidad de Jaen, Campus Las Lagunillas s/n, A3, 23071 Jaen (Spain)

2011-09-01T23:59:59.000Z

168

Observations of Gamma Ray Bursts with AGILE  

E-Print Network (OSTI)

The AGILE satellite, in orbit since 2007, localized up to October 2009 about 1 Gamma Ray Burst (GRB) per month with the hard X-ray imager SuperAGILE (18 - 60 keV) (with a rate reduced by a factor 2-3 in spinning mode) and is detecting around 1 GRB per week with the non-imaging Mini-Calorimeter (MCAL, 0.35 - 100 MeV). Up to October 2011 the AGILE Gamma Ray Imaging Detector firmly detected four GRBs in the energy band between 20 MeV and few GeV. In this paper we review the status of the GRBs observation with AGILE and discuss the upper limits in the gamma-ray band of the non-detected events.

Longo, F; Del Monte, E; Marisaldi, M; Fuschino, F; Giuliani, A

2011-01-01T23:59:59.000Z

169

CONSTRAINTS ON THE SYNCHROTRON EMISSION MECHANISM IN GAMMA-RAY BURSTS  

Science Conference Proceedings (OSTI)

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} Gamma} gamma}{sub e} 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.

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

170

Gamma-Ray Bursts: Jets and Energetics  

E-Print Network (OSTI)

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.

D. A. Frail

2003-11-12T23:59:59.000Z

171

A Shotgun Model for Gamma Ray Bursts  

E-Print Network (OSTI)

We propose that gamma ray bursts (GRBs) are produced by a shower of heavy blobs running into circumstellar material at highly relativistic speeds. The gamma ray emission is produced in the shocks these bullets drive into the surrounding medium. The short term variability seen in GRBs is set by the slowing-down time of the bullets while the overall duration of the burst is set by the lifetime of the central engine. A requirement of this model is that the ambient medium be dense, consistent with a strong stellar wind. The efficiency of the burst can be relatively high.

S. Heinz; M. C. Begelman

1999-08-03T23:59:59.000Z

172

Redshift indicators for gamma-ray bursts  

E-Print Network (OSTI)

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.

J-L. Atteia

2005-05-04T23:59:59.000Z

173

A supersymmetric model of gamma ray bursts  

E-Print Network (OSTI)

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.

L. Clavelli; G. Karatheodoris

2004-03-22T23:59:59.000Z

174

VHE Gamma-ray Supernova Remnants  

SciTech Connect

Increasing observational evidence gathered especially in X-rays and {gamma}-rays during the course of the last few years support the notion that Supernova remnants (SNRs) are Galactic particle accelerators up to energies close to the ''knee'' in the energy spectrum of Cosmic rays. This review summarizes the current status of {gamma}-ray observations of SNRs. Shell-type as well as plerionic type SNRs are addressed and prospect for observations of these two source classes with the upcoming GLAST satellite in the energy regime above 100 MeV are given.

Funk, Stefan; /KIPAC, Menlo Park

2007-01-22T23:59:59.000Z

175

Status of the Milagro $\\gamma$ Ray Observatory  

E-Print Network (OSTI)

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.

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

176

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

E-Print Network (OSTI)

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.

Pijushpani Bhattacharjee; Nayantara Gupta

2003-05-12T23:59:59.000Z

177

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

E-Print Network (OSTI)

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

Bandstra, Mark ShenYu

2010-01-01T23:59:59.000Z

178

Gamma-ray bursts: a Centauro's cry?  

E-Print Network (OSTI)

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.

Z. K. Silagadze

2003-03-04T23:59:59.000Z

179

Galactic Models of Gamma-Ray Bursts  

E-Print Network (OSTI)

We describe observational evidence and theoretical calculations which support the high velocity neutron star model of gamma-ray bursts. We estimate the energetic requirements in this model, and discuss possible energy sources. we also consider radiative processes involved in the bursts.

Donald Q. Lamb; Tomasz Bulik; Paolo S. Coppi

1995-08-20T23:59:59.000Z

180

Delayed Nickel Decay in Gamma Ray Bursts  

E-Print Network (OSTI)

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.

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

2002-05-19T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Neutrino Balls and Gamma-Ray Bursts  

E-Print Network (OSTI)

We propose a mechanism by which the neutrino emission from a supernova-type explosion can be converted into a gamma-ray burst of total energy $\\sim 10^{50}$ ergs. This occurs naturally if the explosion is situated inside a ball of trapped neutrinos, which in turn may lie at a galactic core. There are possible unique signatures of this scenario.

B. Holdom; R. A. Malaney

1993-06-17T23:59:59.000Z

182

Bremsstrahlung gamma rays from light Dark Matter  

E-Print Network (OSTI)

We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting O(10) GeV mass range. Especially from directions close to the Galactic Plane, the expected gamma-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process on the interstellar gas by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is the dominant component of the gamma-ray spectrum for some cases. We also find that, in regions in which bremsstrahlung dominates energy losses, the related gamma-ray emission is only moderately sensitive to possible large variations in the gas density. Still, we stress that, for computing precise spectra in the (sub-)GeV range, it is important to obtain a reliable description of the inner Galaxy gas distribution as well as to compute self-consistently the gamma emission and the solution to the diffusion-loss equation. For example, these are crucial issues to quantify and interpret meaningfully gamma-ray map `residuals' in terms of (light) DM annihilations.

Marco Cirelli; Pasquale D. Serpico; Gabrijela Zaharijas

2013-07-26T23:59:59.000Z

183

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

E-Print Network (OSTI)

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.

Tomonori Totani

1998-10-14T23:59:59.000Z

184

Gamma-Ray Bursts Nuclear Test Ban Treaty, 1963  

E-Print Network (OSTI)

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

Harrison, Thomas

185

The Biggest Bangs The Mystery of Gamma-Ray Bursts,  

E-Print Network (OSTI)

wide field of view and high duty cycle Milagro is uniquely capable of searching for gamma-ray bursts of gamma-ray bursts have come from observa- tions of afterglows over a wide spectral range. This has allowed detailed modeling of gamma-ray burst afterglow properties both as a function of time

Katz, Jonathan I.

186

The Biggest Bangs The Mystery of Gamma-Ray Bursts,  

E-Print Network (OSTI)

Physique www.sciencedirect.com Gamma-ray burst studies in the SVOM era / �tude des sursauts gamma à l s t r a c t Article history: Available online 13 April 2011 Keywords: Gamma-rays, bursts Stars Black by Elsevier Masson SAS. All rights reserved. 1. Introduction The field of gamma-ray bursts (GRBs) has rapidly

Katz, Jonathan I.

187

VERY HIGH ENERGY {gamma}-RAY EMISSION FROM PASSIVE SUPERMASSIVE BLACK HOLES: CONSTRAINTS FOR NGC 1399  

Science Conference Proceedings (OSTI)

Very high energy (VHE, >100 GeV) {gamma}-rays are expected to be emitted from the vicinity of supermassive black holes (SMBHs), irrespective of their activity state. In the magnetosphere of rotating SMBH, efficient acceleration of charged particles can take place through various processes. These particles could reach energies up to E {approx} 10{sup 19} eV. VHE {gamma}-ray emission from these particles is then feasible via leptonic or hadronic processes. Therefore, passive systems, where the lack of a strong photon field allows the VHE {gamma}-rays to escape, are expected to be detected by Cherenkov telescopes. We present results from recent VHE experiments on the passive SMBH in the nearby elliptical galaxy NGC 1399. No {gamma}-ray signal has been found, neither by the H.E.S.S. experiment nor in the Fermi data analyzed here. We discuss possible implications for the physical characteristics of the system. We conclude that in a scenario where particles are accelerated in vacuum gaps in the magnetosphere, only a fraction {approx}0.3 of the gap is available for particle acceleration, indicating that the system is unlikely to be able to accelerate protons up to E {approx} 10{sup 19} eV.

Pedaletti, G.; Wagner, S. J. [Landessternwarte, Universitaet Heidelberg, Koenigstuhl, D-69117 Heidelberg (Germany); Rieger, F. M., E-mail: gpedalet@lsw.uni-heidelberg.de [Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, D-69029 Heidelberg (Germany)

2011-09-10T23:59:59.000Z

188

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

Science Conference Proceedings (OSTI)

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.

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

189

Peculiarly Narrow SED of GRB 090926B with MAXI and Fermi/GBM  

E-Print Network (OSTI)

The monitor of all-sky X-ray image (MAXI) Gas Slit Camera (GSC) on the International Space Station (ISS) detected a gamma-ray burst (GRB) on 2009, September 26, GRB\\,090926B. This GRB had extremely hard spectra in the X-ray energy range. Joint spectral fitting with the Gamma-ray Burst Monitor on the Fermi Gamma-ray Space Telescope shows that this burst has peculiarly narrow spectral energy distribution and is represented by Comptonized blackbody model. This spectrum can be interpreted as photospheric emission from the low baryon-load GRB fireball. Calculating the parameter of fireball, we found the size of the base of the flow $r_0 = (4.3 \\pm 0.9) \\times 10^{9} \\, Y^{\\prime \\, -3/2}$ cm and Lorentz factor of the plasma $\\Gamma = (110 \\pm 10) \\, Y^{\\prime \\, 1/4}$, where $Y^{\\prime}$ is a ratio between the total fireball energy and the energy in the blackbody component of the gamma-ray emission. This $r_0$ is factor of a few larger, and the Lorentz factor of 110 is smaller by also factor of a few than other bu...

Serino, Motoko; Kawai, Nobuyuki; Nakagawa, Yujin E; Ueda, Yoshihiro; Mihara, Tatehiro; Nakahira, Satoshi; Eguchi, Satoshi; Hiroi, Kazuo; Ishikawa, Masaki; Isobe, Naoki; Kimura, Masashi; Kitayama, Hiroki; Kohama, Mitsuhiro; Matsumura, Takanori; Matsuoka, Masaru; Morii, Mikio; Nakajima, Motoki; Negoro, Hitoshi; Shidatsu, Megumi; Sootome, Tetsuya; Sugimori, Kousuke; Sugizaki, Mutsumi; Suwa, Fumitoshi; Toizumi, Takahiro; Tomida, Hiroshi; Tsuboi, Yohko; Tsunemi, Hiroshi; Ueno, Shiro; Usui, Ryuichi; Yamamoto, Takayuki; Yamaoka, Kazutaka; Yamauchi, Makoto; Yamazaki, Kyohei

2011-01-01T23:59:59.000Z

190

Gamma Ray Bursts And Data Challenge One: Searching GRB in One Week of Simulated GLAST LAT Data  

SciTech Connect

GLAST (Gamma-ray Large Area Space Telescope) is a gamma-ray astronomy mission that will be launched in mid 2007. The main instrument is the LAT (Large Area Telescope), a pair conversion telescope with sensitivity in the range 20 MeV-300 GeV. Data Challenge One (DC1) was the simulation of one week of observation of the entire gamma-ray sky by the LAT detector. the simulated data was similar to the real data, which allowed for the development of scientific software. In this paper they present the GRB simulations and the detection algorithms developed by the GLAST GRB and Solar Flare Science Team.

Longo, F.; Omodei, N.; Band, D.; Bonnell, J.T.; Brigida, M.; Cohen-Tanugi, J.; Giannitrapani, R.; Kamae, T.; Norris, J.P.; Winai, M.; /Trieste U. /INFN, Trieste /Siena U. /INFN, Pisa /NASA, Goddard /Bari U. /INFN, Bari /SLAC /Udine U.

2006-02-22T23:59:59.000Z

191

SGARFACE: A Novel Detector For Microsecond Gamma Ray Bursts  

E-Print Network (OSTI)

The Short GAmma Ray Front Air Cherenkov Experiment (SGARFACE) is operated at the Whipple Observatory utilizing the Whipple 10m gamma-ray telescope. SGARFACE is sensitive to gamma-ray bursts of more than 100MeV with durations from 100ns to 35us and provides a fluence sensitivity as low as 0.8 gamma-rays per m^2 above 200MeV (0.05 gamma-rays per m^2 above 2GeV) and allows to record the burst time structure.

S. LeBohec; F. Krennrich; G. Sleege

2005-01-11T23:59:59.000Z

192

Neutron-driven gamma-ray laser  

DOE Patents (OSTI)

A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 {angstrom} when subjected to an intense neutron flux of about 400 eV neutrons. A 250 {angstrom} thick layer of Be is provided between two layers of 100 {angstrom} 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.

Bowman, C.D.

1989-03-28T23:59:59.000Z

193

Neutron-driven gamma-ray laser  

DOE Patents (OSTI)

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.

Bowman, Charles D. (Los Alamos, NM)

1990-01-01T23:59:59.000Z

194

THE GAMMA-RAY BURST MYSTERY  

E-Print Network (OSTI)

Gamma-ray bursts are transient events from beyond the solar system. Besides the allure of their mysterious origin, bursts are physically fascinating because they undoubtedly require exotic physics. Optical transients coincident with burst positions show that some, and probably all, bursts originate at cosmological distances, and not from a large Galactic halo. Observations of these events ’ spectral and temporal behavior will guide and constrain the study of the physical processes producing this extragalactic phenomenon. 1

David L. Band

1997-01-01T23:59:59.000Z

195

Lecture 7Lecture 7 The GammaThe Gamma--RayRay  

E-Print Network (OSTI)

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

196

A Link between Prompt Optical and Prompt Gamma-Ray Emission in Gamma-Ray Bursts  

E-Print Network (OSTI)

The prompt optical emission that arrives with gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with the surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium.

W. T. Vestrand; P. R. Wozniak; J. A. Wren; E. E. Fenimore; T. Sakamoto; R. R. White; D. Casperson; H. Davis; S. Evans; M. Galassi; K. E. McGowan; J. A. Schier; J. W. Asa; S. D. Barthelmy; J. R. Cummings; N. Gehrels; D. Hullinger; H. A. Krimm; C. B. Markwardt; K. McLean; D. Palmer; A. Parsons; J. Tueller

2005-03-23T23:59:59.000Z

197

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

E-Print Network (OSTI)

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.

A. E. McCoy

2012-01-04T23:59:59.000Z

198

GAMMA-RAY ACTIVITY IN THE CRAB NEBULA: THE EXCEPTIONAL FLARE OF 2011 APRIL  

SciTech Connect

The Large Area Telescope on board the Fermi satellite observed a gamma-ray flare in the Crab Nebula lasting for approximately nine days in April of 2011. The source, which at optical wavelengths has a size of Almost-Equal-To 11 lt-yr across, doubled its gamma-ray flux within eight hours. The peak photon flux was (186 {+-} 6) Multiplication-Sign 10{sup -7} cm{sup -2} s{sup -1} above 100 MeV, which corresponds to a 30-fold increase compared to the average value. During the flare, a new component emerged in the spectral energy distribution, which peaked at an energy of (375 {+-} 26) MeV at flare maximum. The observations imply that the emission region was likely relativistically beamed toward us and that variations in its motion are responsible for the observed spectral variability.

Buehler, R.; Blandford, R. D.; Charles, E.; Chiang, J.; Funk, S.; Kerr, M.; Massaro, F.; Romani, R. W. [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); Scargle, J. D. [Space Sciences Division, NASA Ames Research Center, Moffett Field, CA 94035-1000 (United States); Baldini, L. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Baring, M. G. [Rice University, Department of Physics and Astronomy, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Belfiore, A.; Saz Parkinson, P. M. [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); D'Ammando, F. [IASF Palermo, 90146 Palermo (Italy); Dermer, C. D.; Grove, J. E. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Harding, A. K.; Hays, E. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mazziotta, M. N. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70126 Bari (Italy); Tennant, A. F., E-mail: buehler@stanford.edu, E-mail: rdb3@stanford.edu, E-mail: Jeffrey.D.Scargle@nasa.gov [NASA, Marshall Space Flight Center, Huntsville, AL 35812 (United States); and others

2012-04-10T23:59:59.000Z

199

EPISODIC JETS AS THE CENTRAL ENGINE OF GAMMA-RAY BURSTS  

SciTech Connect

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.

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

200

Phase-space methods in nuclear reactions around the Fermi energy  

E-Print Network (OSTI)

Some prescriptions for in-medium complex particle production in nuclear reactions are proposed. They have been implemented in two models to simulate nucleon-nucleus (nIPSE) and nucleus-nucleus (HIPSE) reactions around the Fermi energy \\cite{Lac04,Lac05}. Our work emphasizes the effect of randomness in cluster formation, the importance of the nucleonic Fermi motion as well as the role of conservation laws. The key role of the phase-space exploration before and after secondary decay is underlined. This is illustrated in the case of two debated issues: the memory loss of the entrance channel in central collisions and the $(N,Z)$ partitions after the pre-equilibrium stage.

Denis Lacroix; Dominique Durand; Gregory Lehaut; Olivier Lopez; Emmanuel Vient

2006-01-18T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Gamma-ray spectra of hexane in gas phase and liquid phase  

E-Print Network (OSTI)

Theoretical gamma-ray spectra of molecule hexane have been calculated and compared with the experimental results in both gas (Surko et al, 1997) and liquid (Kerr et al, 1965) phases. The present study reveals that in gas phase not all valence electrons of hexane exhibit the same probability to annihilate a positron. Only the positrophilic electrons in the valence space dominate the gamma-ray spectra, which are in good agreement with the gas phase measurement. When hexane is confined in liquid phase, however, the intermolecular interactions ultimately eliminate the free molecular orientation and selectivity for the positrophilic electrons in the gas phase. As a result, the gamma-ray spectra of hexane become an averaged contribution from all valence electrons, which is again in agreement with liquid phase measurement. The roles of the positrophilic electrons in annihilation process for gas and liquid phases of hexane have been recognized for the first time in the present study.

Xiaoguang Ma; Feng Wang

2012-11-01T23:59:59.000Z

202

Gamma-ray spectra of hexane in gas phase and liquid phase  

E-Print Network (OSTI)

Theoretical gamma-ray spectra of molecule hexane have been calculated and compared with the experimental results in both gas (Surko et al, 1997) and liquid (Kerr et al, 1965) phases. The present study reveals that in gas phase not all valence electrons of hexane exhibit the same probability to annihilate a positron. Only the positrophilic electrons in the valence space dominate the gamma-ray spectra, which are in good agreement with the gas phase measurement. When hexane is confined in liquid phase, however, the intermolecular interactions ultimately eliminate the free molecular orientation and selectivity for the positrophilic electrons in the gas phase. As a result, the gamma-ray spectra of hexane become an averaged contribution from all valence electrons, which is again in agreement with liquid phase measurement. The roles of the positrophilic electrons in annihilation process for gas and liquid phases of hexane have been recognized for the first time in the present study.

Ma, Xiaoguang

2012-01-01T23:59:59.000Z

203

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

E-Print Network (OSTI)

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.

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

1998-05-19T23:59:59.000Z

204

Gamma-Ray Bursts observed by INTEGRAL  

E-Print Network (OSTI)

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.

S. Mereghetti

2003-12-12T23:59:59.000Z

205

Neutrino Event Rates from Gamma Ray Bursts  

E-Print Network (OSTI)

We recalculate the diffuse flux of high energy neutrinos produced by Gamma Ray Bursts (GRB) in the relativistic fireball model. Although we confirm that the average single burst produces only ~10^{-2} high energy neutrino events in a detector with 1 km^2 effective area, i.e. about 10 events per year, we show that the observed rate is dominated by burst-to-burst fluctuations which are very large. We find event rates that are expected to be larger by one order of magnitude, likely more, which are dominated by a few very bright bursts. This greatly simplifies their detection.

F. Halzen; D. W. Hooper

1999-08-12T23:59:59.000Z

206

Can Naked Singularities Yield Gamma Ray Bursts?  

E-Print Network (OSTI)

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.

H. M. Antia

1998-07-09T23:59:59.000Z

207

RECONSTRUCTING THE {gamma}-RAY PHOTON OPTICAL DEPTH OF THE UNIVERSE TO z {approx} 4 FROM MULTIWAVELENGTH GALAXY SURVEY DATA  

Science Conference Proceedings (OSTI)

We reconstruct the {gamma}-ray opacity of the universe out to z {approx}gamma}{gamma} optical depth out to several TeV. Here, we use the same database as Helgason et al. where the extragalactic background light was reconstructed from LFs out to 4.5 {mu}m and was shown to recover observed galaxy counts to high accuracy. We extend our earlier library of LFs to 25 {mu}m such that it covers the energy range of pair production with {gamma}-rays (1) in the entire Fermi/LAT energy range, and (2) at higher TeV energies probed by ground-based Cherenkov telescopes. In the absence of significant contributions to the cosmic diffuse background from unknown populations, such as the putative Population III era sources, the universe appears to be largely transparent to {gamma}-rays at all Fermi/LAT energies out to z {approx} 2 whereas it becomes opaque to TeV photons already at z {approx}gamma-ray burst and blazar data shows that there is room for significant emissions originating in the first stars era.

Helgason, Kari [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Kashlinsky, Alexander, E-mail: kari@astro.umd.edu, E-mail: alexander.kashlinsky@nasa.gov [Observational Cosmology Laboratory, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-10-10T23:59:59.000Z

208

GAMQUEST, a Computer Program to Identify Gamma Rays  

NLE Websites -- All DOE Office Websites (Extended Search)

GAMQUEST GAMQUEST A Computer Program to Identify Gamma Rays Edgardo Browne, Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 EBROWNE@LBL.Gov Table of Contents Introduction. Program Access and Output Files. How to Run GAMQUEST. From Individual Accounts. From Guest Account. Gamma-Ray Data. GAMQUEST, a Tool for Applied Research. Searching Strategies. Examples. Neutron Activation Analysis. Gamma-Ray Spectrum Between 100 and 800 keV. Gamma-Ray Spectrum Between 800 and 1600 keV. A List of X Rays and Gamma Rays from the Decay of 192Ir (74 hr). Run GAMQUEST from Guest Account Acknowledgments. References. 1. Introduction. The characteristic energies and intensities of gamma rays emitted by radioactive isotopes are commonly used as fingerprints for isotope

209

Gamma-ray burst interaction with dense interstellar medium  

E-Print Network (OSTI)

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.

Maxim Barkov; Gennady Bisnovatyi-Kogan

2004-10-07T23:59:59.000Z

210

X-Ray Observations of Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

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.

Filippo Frontera

2004-06-25T23:59:59.000Z

211

Nuclear Criticality as a Contributor to Gamma Ray Burst Events  

E-Print Network (OSTI)

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.

Robert Bruce Hayes

2013-01-15T23:59:59.000Z

212

The Multiwavelength Approach to Unidentified Gamma-Ray Sources  

E-Print Network (OSTI)

As the highest-energy photons, gamma rays have an inherent interest to astrophysicists and particle physicists studying high-energy, nonthermal processes. Gamma-ray telescopes complement those at other wavelengths, especially radio, optical, and X-ray, providing the broad, mutiwavelength coverage that has become such a powerful aspect of modern astrophysics. Multiwavelength techniques of various types have been developed to help identify and explore unidentified gamma-ray sources. This overview summarizes the ideas behind several of these methods.

David J. Thompson

2004-07-20T23:59:59.000Z

213

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

E-Print Network (OSTI)

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.

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

1994-11-25T23:59:59.000Z

214

DIFFUSE PeV NEUTRINOS FROM GAMMA-RAY BURSTS  

SciTech Connect

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.

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

215

THE DIFFUSE GAMMA-RAY BACKGROUND FROM TYPE Ia SUPERNOVAE  

SciTech Connect

The origin of the diffuse extragalactic gamma-ray background (EGB) has been intensively studied but remains unsettled. Current popular source candidates include unresolved star-forming galaxies, starburst galaxies, and blazars. In this paper, we calculate the EGB contribution from the interactions of cosmic rays accelerated by Type Ia supernovae (SNe), extending earlier work that only included core-collapse SNe. We consider Type Ia events not only in star-forming galaxies, but also in quiescent galaxies that lack star formation. In the case of star-forming galaxies, consistently including Type Ia events makes little change to the star-forming EGB prediction, so long as both SN types have the same cosmic-ray acceleration efficiencies in star-forming galaxies. Thus, our updated EGB estimate continues to show that star-forming galaxies can represent a substantial portion of the signal measured by Fermi. In the case of quiescent galaxies, conversely, we find a wide range of possibilities for the EGB contribution. The dominant uncertainty we investigated comes from the mass in hot gas in these objects, which provides targets for cosmic rays; total gas masses are as yet poorly known, particularly at larger radii. Additionally, the EGB estimation is very sensitive to the cosmic-ray acceleration efficiency and confinement, especially in quiescent galaxies. In the most optimistic allowed scenarios, quiescent galaxies can be an important source of the EGB. In this case, star-forming galaxies and quiescent galaxies together will dominate the EGB and leave little room for other contributions. If other sources, such as blazars, are found to have important contributions to the EGB, then either the gas mass or cosmic-ray content of quiescent galaxies must be significantly lower than in their star-forming counterparts. In any case, improved Fermi EGB measurements will provide important constraints on hot gas and cosmic rays in quiescent galaxies.

Lien, Amy; Fields, Brian D. [Department of Physics, University of Illinois, Urbana, IL 61801 (United States)

2012-03-10T23:59:59.000Z

216

SENSITIVITY OF BLIND PULSAR SEARCHES WITH THE FERMI LARGE AREA TELESCOPE  

SciTech Connect

We quantitatively establish the sensitivity to the detection of young to middle-aged, isolated, gamma-ray pulsars through blind searches of Fermi Large Area Telescope (LAT) data using a Monte Carlo simulation. We detail a sensitivity study of the time-differencing blind search code used to discover gamma-ray pulsars in the first year of observations. We simulate 10,000 pulsars across a broad parameter space and distribute them across the sky. We replicate the analysis in the Fermi LAT First Source Catalog to localize the sources, and the blind search analysis to find the pulsars. We analyze the results and discuss the effect of positional error and spin frequency on gamma-ray pulsar detections. Finally, we construct a formula to determine the sensitivity of the blind search and present a sensitivity map assuming a standard set of pulsar parameters. The results of this study can be applied to population studies and are useful in characterizing unidentified LAT sources.

Dormody, M.; Johnson, R. P.; Atwood, W. B.; Belfiore, A.; Razzano, M.; Saz Parkinson, P. M. [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); Grenier, I. A. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Johnson, T. J., E-mail: dormody@scipp.ucsc.edu [National Academy of Sciences, Washington, DC 20001 (United States)

2011-12-01T23:59:59.000Z

217

Inelastic cross sections from gamma-ray measurements  

Science Conference Proceedings (OSTI)

Measurements of gamma rays following neutron induced reactions have been studied with the Germanium Array for Neutron-induced Excitations (GEANIE) at the Los Alamos Neutron Science Center (LANSCE) for many years. Gamma-ray excitation functions and coincidence studies provide insight into nuclear reaction mechanisms as well as expanding our knowledge of energy levels and gamma-rays. Samples studied with Ge detectors at LANSCE range from Be to Pu. Fe, Cr and Ti have been considered for use as reference cross sections. An overview of the measurements and efforts to create a reliable neutron-induced gamma-ray reference cross section will be presented.

Nelson, Ronald Owen [Los Alamos National Laboratory

2010-12-06T23:59:59.000Z

218

The Diverse Environments of Gamma-Ray Bursts.  

E-Print Network (OSTI)

??I present results from several years of concerted observations of the afterglows and host galaxies of gamma-ray bursts (GRBs), the most energetic explosions in the… (more)

Perley, Daniel Alan

2011-01-01T23:59:59.000Z

219

X-ray Flares in Gamma-Ray Bursts.  

E-Print Network (OSTI)

??Data from the Swift mission have now shown that flares are a common component of Gamma-Ray Burst afterglows, appearing in roughly 50% of GRBs to… (more)

Morris, David

2008-01-01T23:59:59.000Z

220

Astrophysical and Astrobiological effects of Gamma-Ray Bursts.  

E-Print Network (OSTI)

??O presente trabalho tem o objetivo principal de compreender os possíveis efeitos da radiação energética de um evento de Gamma-Ray Burst (GRB) sobre o meio… (more)

Douglas Galante

2009-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Two Classes of Gamma-Ray Bursts  

E-Print Network (OSTI)

If gamma-ray bursts are at cosmological distances, as suggested by their isotropy on the sky and the comparative deficiency of weak bursts, then they represent radiated energies of ? 1051 erg, and imply the release of an even greater energy. Only neutron stars and black holes have binding energies sufficient to power such extraordinarily violent and energetic events. General considerations of neutrino opacity imply1 that the escape of a neutron star’s (or black hole’s) binding energy requires a time of about 10 sec, as shown by the observed duration of neutrino emission from SN1987A. The distribution of durations of gamma-ray bursts is known2 to be bimodal, with one peak between 10 and 100 sec and the other between 0.1 and 1 sec. We hypothesize that the durations of the longer bursts may be explained as the result of the diffusion of energy, by means of neutrinos, from a forming neutron star or black hole, but that the brevity of the shorter bursts requires different physics. An alternative hypothesis supposes that all bursts (excepting soft gamma repeaters, which we do not discuss) represent a single class of events, whose differing durations reflect differences in one or more parameters. These two hypotheses may be tested using data from the recently released 3B Catalogue3.

J. I. Katz; L. M. Canel

1995-01-01T23:59:59.000Z

222

Supermassive Objects as Gamma-Ray Bursters  

E-Print Network (OSTI)

We propose that the gravitational collapse of supermassive objects ($ M\\ga 10^4 M_\\odot$), either as relativistic star clusters or as single supermassive stars (which may result from stellar mergers in dense star clusters), could be a cosmological source of $\\gamma$-ray bursts. These events could provide the seeds of the supermassive black holes observed at the center of many galaxies. Collapsing supermassive objects will release a fraction of their huge gravitational binding energy as thermal neutrino pairs. We show that the accompanying neutrino/antineutrino annihilation-induced heating could drive electron/positron ``fireball'' formation, relativistic expansion, and associated $\\gamma$-ray emission. The major advantage of this model is its energetics: supermassive object collapses are far more energetic than solar mass-scale compact object mergers; therefore, the conversion of gravitational energy to fireball kinetic energy in the supermassive object scenario need not be highly efficient, nor is it necessary to invoke directional beaming. The major weakness of this model is difficulty in avoiding a baryon loading problem for one dimensional collapse scenarios.

George M. Fuller; Xiangdong Shi

1997-11-04T23:59:59.000Z

223

No Evidence for Gamma-Ray Burst/Abell Cluster or Gamma- Ray Burst/Radio-Quiet Quasar Correlations  

E-Print Network (OSTI)

We examine the recent claims that cosmic gamma-ray bursts are associated with either radio-quiet quasars or Abell clusters. These associations were based on positional coincidences between cataloged quasars or Abell clusters, and selected events from the BATSE 3B catalog of gamma-ray bursts. We use a larger sample of gamma-ray bursts with more accurate positions, obtained by the 3rd Interplanetary Network, to re-evaluate these possible associations. We find no evidence for either.

K. Hurley; D. H. Hartmann; C. Kouveliotou; R. M. Kippen; J. Laros; T. Cline; M. Boer

1998-11-28T23:59:59.000Z

224

GeV EMISSION FROM COLLISIONAL MAGNETIZED GAMMA-RAY BURSTS  

Science Conference Proceedings (OSTI)

Magnetic fields may play a dominant role in gamma-ray bursts, and recent observations by Fermi 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.

Meszaros, P. [Department of Astronomy and Astrophysics, Department of Physics and Center for Particle Astrophysics, 525 Davey Lab., Pennsylvania State University, University Park, PA 16802 (United States); Rees, M. J. [Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA (United Kingdom)

2011-06-01T23:59:59.000Z

225

Massive Stars in Colliding Wind Systems: the High-Energy Gamma-Ray Perspective  

SciTech Connect

Colliding winds of massive stars in binary systems are viable candidates for non-thermal high-energy photon emission. Long since, coincidences between massive star systems/associations and {gamma}-ray sources have been noted. Now, with the sensitivity of the Fermi Gamma Ray Observatory and current very-high-energy (VHE) Cherenkov instruments, will it be possible to sensibly probe these systems as high-energy emitters.We will summarize the characteristics and broadband predictions of generic optically thin emission models in the observables accessible at GeV and TeV energies. The ability to constrain orbital parameters of massive star-star binaries through GeV-to-TeV observations is discussed. As an example we will present orbital parameter constraints for the nearby Wolf-Rayet binary system WR 147 based on recently published VHE flux limits. Combining our broadband emission model with the cataloged binaries systems and their individual parameters allows us to conclude on the population of massive star-star systems at high-energy {gamma}-rays.

Reimer, Anita; Reimer, Olaf; /Stanford U., HEPL /KIPAC, Menlo Park

2011-11-23T23:59:59.000Z

226

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

E-Print Network (OSTI)

), 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

Enomoto, Ryoji

227

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

E-Print Network (OSTI)

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

California at Berkeley, University of

228

THE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT  

E-Print Network (OSTI)

), 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

Enomoto, Ryoji

229

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

E-Print Network (OSTI)

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

Zhang, Bing

230

The Electron Injection Spectrum Determined by Anomalous Excesses in Cosmic Ray, Gamma Ray, and Microwave Signals  

E-Print Network (OSTI)

Recent cosmic ray, gamma ray, and microwave signals observed by Fermi, PAMELA, and WMAP indicate an unexpected primary source of e+e- at 10-1000 GeV. We fit these data to "standard backgrounds" plus a new source, assumed to be a separable function of position and energy. For the spatial part, we consider three cases: annihilating dark matter, decaying dark matter, and pulsars. In each case, we use GALPROP to inject energy in log-spaced energy bins and compute the expected cosmic-ray and photon signals for each bin. We then fit a linear combination of energy bins, plus backgrounds, to the data. We use a non-parametric fit, with no prior constraints on the spectrum except smoothness and non-negativity. In addition, we consider arbitrary modifications to the energy spectrum of the "ordinary" primary source function, fixing its spatial part, finding this alone to be inadequate to explain the PAMELA or WMAP signals. We explore variations in the fits due to choice of magnetic field, primary electron injection index, spatial profiles, propagation parameters, and fit regularization method. Dark matter annihilation fits well, where our fit finds a mass of ~1 TeV and a boost factor times energy fraction of ~70. While it is possible for dark matter decay and pulsars to fit the data, unconventionally high magnetic fields and radiation densities are required near the Galactic Center to counter the relative shallowness of the assumed spatial profiles. We also fit to linear combinations of these three scenarios, though the fit is much less constrained.

Tongyan Lin; Douglas P. Finkbeiner; Gregory Dobler

2010-04-07T23:59:59.000Z

231

Variability of EGRET Gamma-Ray Sources  

E-Print Network (OSTI)

The variability of the high-energy gamma ray sources in the Third EGRET catalog is analyzed by a new method. We re-analyze the EGRET data to calculate a likelihood function for the flux of each source in each observation, both for detections and upper limits. These functions can be combined in a uniform manner with a simple model of the flux distribution to characterize the flux variation by a confidence interval for the relative standard deviation of the flux. The main result is a table of these values for almost all the cataloged sources. As expected, the identified pulsars are steady emitters and the blazars are mostly highly variable. The unidentified sources are heterogeneous, with greater variation at higher Galactic latitude. There is an indication that pulsar wind nebulae are associated with variable sources. There is a population of variable sources along the Galactic plane, concentrated in the inner spiral arms.

P. L. Nolan; W. F. Tompkins; I. A. Grenier; P. F. Michelson

2003-07-10T23:59:59.000Z

232

Short Gamma-Ray Bursts Are Different  

E-Print Network (OSTI)

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.

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

2001-05-07T23:59:59.000Z

233

COMPTEL Observations of Gamma-ray Bursts  

E-Print Network (OSTI)

INTRODUCTION The origin of cosmic g-ray bursts is as mysterious today as it was when they were discovered more than 25 years ago. Despite a wealth of new observational data obtained with the BATSE instrument on board the Compton Gamma Ray Observatory, many of the fundamental questions remain unanswered. For instance, although BATSE has provided a tremendous statistical advantage (allowing the most accurate measurement of the spatial isotropy and inhomogeneity of burst sources ), its limited angular resolution and spectral range have given us an incomplete picture of the small-scale angular source distribution and high energy emission properties. 2,3 Furthermore, the limited angular resolution has also made it difficult to search for burst counterparts at other wavelengths. The COMPTEL instrument on board Compton measures the locations and spectra (0.75-30 MeV) of several strong g-ray bursts per year which occur within the ~1 sr fieldof -view of the main ("telescope") instrument.

Kippen Ryan Connors; R. M. Kippen; B J. Ryan; B A. Connors; B M. Mcconnell; V. Schönfelder; C J. Greiner; C M. Varendorff; W. Collmar; C W. Hermsen; D L. Kuiper; D C. Winkler; L. O. Hanlon E; K. S. O’flaherty E

1995-01-01T23:59:59.000Z

234

Millisecond Proto-Magnetars & Gamma Ray Bursts  

E-Print Network (OSTI)

In the seconds after core collapse and explosion, a thermal neutrino-driven wind emerges from the cooling, deleptonizing newly-born neutron star. If the neutron star has a large-scale magnetar-strength surface magnetic field and millisecond rotation period, then the wind is driven primarily by magneto-centrifugal slinging, and only secondarily by neutrino interactions. The strong magnetic field forces the wind to corotate with the stellar surface and the neutron star's rotational energy is efficiently extracted. As the neutron star cools, and the wind becomes increasingly magnetically-dominated, the outflow becomes relativistic. Here I review the millisecond magnetar model for long-duration gamma ray bursts and explore some of the basic physics of neutrino-magnetocentrifugal winds. I further speculate on some issues of collimation and geometry in the millisecond magnetar model.

Todd A. Thompson

2005-04-27T23:59:59.000Z

235

Constraining Lorentz violations with Gamma Ray Bursts  

E-Print Network (OSTI)

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.

Maria Rodriguez Martinez; Tsvi Piran

2006-01-10T23:59:59.000Z

236

Gravitational Waves versus Electromagnetic Emission in Gamma-Ray Bursts  

E-Print Network (OSTI)

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 electromagnetic emission in a Gamma-Ray Burst.

Jorge A. Rueda; Remo Ruffini

2012-05-31T23:59:59.000Z

237

A simple empirical redshift indicator for gamma-ray bursts  

E-Print Network (OSTI)

We propose a new empirical redshift indicator for gamma-ray bursts. This indicator is easily computed from the gamma-ray burst spectral parameters, and its duration, and it provides ``pseudo-redshifts'' accurate to a factor two. Possible applications of this redshift indicator are briefly discussed.

J-L Atteia

2003-04-17T23:59:59.000Z

238

Semantic image interpretation of gamma ray profiles in petroleum exploration  

Science Conference Proceedings (OSTI)

This paper presents the S-Chart framework, an approach for semantic image interpretation of line charts; and the InteliStrata system, an application for semantic interpretation of gamma ray profiles. The S-Chart framework is structured as a set of knowledge ... Keywords: Gamma ray well log, Ontology, Semantic image interpretation, Stratigraphy, Symbol grounding problem, Visual knowledge

Sandro Rama Fiorini; Mara Abel; Claiton M. S. Scherer

2011-04-01T23:59:59.000Z

239

The Swift Gamma-Ray Burst Mission  

E-Print Network (OSTI)

The Swift mission, scheduled for launch in early 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is the first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts per year and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to determine the origin of GRBs; classify GRBs and search for new types; study the interaction of the ultra-relativistic outflows of GRBs with their surrounding medium; and use GRBs to study the early universe out to z>10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a new-generation wide-field gamma-ray (15-150 keV) detector; a narrow-field X-ray telescope; and a narrow-field UV/optical telescope. Redshift determinations will be made for most bursts. In addition to the primary GRB science, the mission will perform a hard X-ray survey to a sensitivity of ~1 mCrab (~2x10^{-11} erg cm^{-2} s^{-1} in the 15-150 keV band), more than an order of magnitude better than HEAO A-4. A flexible data and operations system will allow rapid follow-up observations of all types of high-energy transients, with rapid data downlink and uplink available through the NASA TDRSS system. The mission is currently funded for 2 years of operations and the spacecraft will have a lifetime to orbital decay of ~8 years. [ABRIDGED

N. Gehrels; G Chincarini; P. Giommi; K. O. Mason; J. A. Nousek; A. A. Wells; N. E. White; S. D. Barthelmy; D. N. Burrows; L. R. Cominsky; K. C. Hurley; F. E. Marshall; P. Meszaros; P. W. A. Roming; Swift Science Team

2004-05-12T23:59:59.000Z

240

LONG GAMMA-RAY TRANSIENTS FROM COLLAPSARS  

Science Conference Proceedings (OSTI)

In the collapsar model for common gamma-ray bursts (GRBs), the formation of a centrifugally supported disk occurs during the first {approx}10 s following the collapse of the iron core in a massive star. This only occurs in a small fraction of massive stellar deaths, however, and requires unusual conditions. A much more frequent occurrence could be the death of a star that makes a black hole and a weak or absent outgoing shock, but in a progenitor that only has enough angular momentum in its outermost layers to make a disk. We consider several cases where this is likely to occur-blue supergiants with low mass-loss rates, tidally interacting binaries involving either helium stars or giant stars, and the collapse to a black hole of very massive pair-instability supernovae. These events have in common the accretion of a solar mass or so of material through a disk over a period much longer than the duration of a common GRB. A broad range of powers is possible, 10{sup 47}-10{sup 50} erg s{sup -1}, and this brightness could be enhanced by beaming. Such events were probably more frequent in the early universe where mass-loss rates were lower. Indeed, this could be one of the most common forms of gamma-ray transients in the universe and could be used to study first generation stars. Several events could be active in the sky at any one time. Recent examples of this sort of event may have been the Swift transients Sw-1644+57, Sw-2058+0516, and GRB 101225A.

Woosley, S. E. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Heger, Alexander, E-mail: woosley@ucolick.org, E-mail: alex@physics.umn.edu [Minnesota Institute of Astrophysics, School of Physics and Astronomy, University of Minnesota, Twin Cities, Minneapolis, MN 55455 (United States)

2012-06-10T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
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241

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

E-Print Network (OSTI)

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.

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

242

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

SciTech Connect

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.

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

243

The Quest for Gamma Rays:The Quest for Gamma Rays: Exploring the Most Violent PlacesExploring the Most Violent Places  

E-Print Network (OSTI)

beyond our Galaxy. Keywords: very high energy gamma rays, pulsar, active galactic nuclei, gamma ray burst as well as about `after glow' of southern gamma ray bursts which BeppoSAX satellite detected with aboutTHE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT WOOMERA TADASHI KIFUNE

244

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

E-Print Network (OSTI)

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

Fynbo, Johan

245

Prompt Optical Observations of Gamma-Ray Bursts  

E-Print Network (OSTI)

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 square degree or better produced no detections. The earliest limiting sensitivity is mROTSE> 13.1 at 10.85 seconds (5 second exposure) after the gamma-ray rise, and the best limit is mROTSE> 16.0 at 62 minutes (897 second exposure). These are the most stringent limits obtained for GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission. Subject headings: gamma rays: bursts, observations 1.

Carl Akerlof; Richard Balsano; Scott Barthelmy; Jeff Bloch; Paul Butterworth; Tom Cline; Ra Fletcher; Galen Gisler; John Heise; Jack Hills; Kevin Hurley; Robert Kehoe; Brian Lee; Stuart Marshall; Tim Mckay; Andrew Pawl; Luigi Piro; John Szymanski; Jim Wren

2000-01-01T23:59:59.000Z

246

Polarization mesurements of gamma ray bursts and axion like particles  

E-Print Network (OSTI)

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.

Andre Rubbia; Alexander Sakharov

2008-09-03T23:59:59.000Z

247

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

Science Conference Proceedings (OSTI)

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.

Fan, Yi-Zhong; Piran, Tsvi

2011-11-29T23:59:59.000Z

248

Coordinate-Space Hartree-Fock-Bogoliubov Solvers for Superfluid Fermi Systems in Large Boxes  

SciTech Connect

The self-consistent Hartree-Fock-Bogoliubov problem in large boxes can be solved accurately in the coordinate space with the recently developed solvers HFB-AX (2D) and MADNESS-HFB (3D). This is essential for the description of superfluid Fermi systems with complicated topologies and significant spatial extend, such as fissioning nuclei, weakly-bound nuclei, nuclear matter in the neutron star rust, and ultracold Fermi atoms in elongated traps. The HFB-AX solver based on B-spline techniques uses a hybrid MPI and OpenMP programming model for parallel computation for distributed parallel computation, within a node multi-threaded LAPACK and BLAS libraries are used to further enable parallel calculations of large eigensystems. The MADNESS-HFB solver uses a novel multi-resolution analysis based adaptive pseudo-spectral techniques to enable fully parallel 3D calculations of very large systems. In this work we present benchmark results for HFB-AX and MADNESS-HFB on ultracold trapped fermions.

Pei, J. C. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Fann, George I [ORNL; Harrison, Robert J [ORNL; Nazarewicz, W. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Hill, Judith C [ORNL; Galindo, Diego A [ORNL; Jia, Jun [ORNL

2012-01-01T23:59:59.000Z

249

Observations of Gamma-Ray Burst Afterglows with the AEOS Burst Camera.  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs), are variable bursts of gamma-ray radiation, that lasts from milliseconds to hundreds of seconds. These bursts of gamma rays are detected in… (more)

Flewelling, Heather Anne

2009-01-01T23:59:59.000Z

250

Feasibility of GRB with TeV gamma ray all sky monitor  

E-Print Network (OSTI)

We discuss feasibility of Gamma ray burst (GRB) with TeV gamma ray all sky monitor and discuss necessity of TeV gamma ray cherenkov all sky monitor.

S. Osone

2003-05-14T23:59:59.000Z

251

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

E-Print Network (OSTI)

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

Kamiya, Kaoru

2011-01-01T23:59:59.000Z

252

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

E-Print Network (OSTI)

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

Achterberg, A.; IceCube Collaboration

2008-01-01T23:59:59.000Z

253

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

E-Print Network (OSTI)

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

2004-01-01T23:59:59.000Z

254

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

E-Print Network (OSTI)

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

Abbasi, R.

2010-01-01T23:59:59.000Z

255

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

E-Print Network (OSTI)

of two classes of gamma-ray bursts. Astrophys. J. 413, 6.V. et al. Host galaxies of gamma-ray bursts: Spectral energyal. Are the hosts of gamma-ray bursts sub-luminous and blue

2006-01-01T23:59:59.000Z

256

Gamma-ray constraints on dark-matter annihilation to electroweak gauge and Higgs bosons  

E-Print Network (OSTI)

Dark-matter annihilation into electroweak gauge and Higgs bosons results in $\\gamma$-ray emission. We use observational upper limits on the fluxes of both line and continuum $\\gamma$-rays from the Milky Way Galactic Center and from Milky Way dwarf companion galaxies to set exclusion limits on allowed dark-matter masses. (Generally, Galactic Center $\\gamma$-ray line search limits from the Fermi-LAT and the H.E.S.S. experiments are most restrictive.) Our limits apply under the following assumptions: a) the dark matter species is a cold thermal relic with present mass density equal to the measured dark-matter density of the universe; b) dark-matter annihilation to standard-model particles is described in the non-relativistic limit by a single effective operator ${\\cal O} \\propto J_{DM}\\cdot J_{SM}$, where $J_{DM}$ is a standard-model singlet current consisting of dark-matter fields (Dirac fermions or complex scalars), and $J_{SM}$ is a standard-model singlet current consisting of electroweak gauge and Higgs bosons; and c) the dark-matter mass is in the range 5 GeV to 20 TeV. We consider, in turn, the 34 possible operators with mass dimension 8 or lower with non-zero s-wave annihilation channels satisfying the above assumptions. Our limits are presented in a large number of figures, one for each of the 34 possible operators; these limits can be grouped into 13 classes determined by the field content and structure of the operators. We also identify three classes of operators (coupling to the Higgs and $SU(2)_L$ gauge bosons) that can supply a 130 GeV line with the desired strength to fit the putative line signal in Fermi data, while saturating the relic density and satisfying all other indirect constraints we consider.

Michael A. Fedderke; Edward W. Kolb; Tongyan Lin; Lian-Tao Wang

2013-10-22T23:59:59.000Z

257

Earth Occultation Imaging of the Low Energy Gamma-Ray Sky with GBM  

E-Print Network (OSTI)

The Earth Occultation Technique (EOT) has been applied to Fermi's Gamma-ray Burst Monitor (GBM) to perform all-sky monitoring for a predetermined catalog of hard X-ray/soft gamma-ray sources. Imaging with a Differential filter using the Earth Occultation Method (IDEOM) has been developed to search for sources not in the catalog, thus completing the catalog and reducing a source of systematic error in EOT. IDEOM is a tomographic imaging method that takes advantage of the orbital precession of the Fermi satellite. Using IDEOM, all-sky images have been generated for ~4 years of GBM data in the 12-50 keV, 50-100 keV and 100-300 keV energy bands in search of sources otherwise unmodeled by the GBM occultation analysis. Analysis resulted in the detection of 43 sources in the 12-50 keV energy band, 23 sources in the 50-100 keV energy band, and 7 sources in the 100-300 keV energy band. IDEOM analysis has resulted in the addition of 16 sources to the GBM-EOT catalog. We also present the first joined averaged spectra fo...

Rodi, J; Case, G L; Camero-Arranz, A; Chaplin, C; Finger, M H; Jenke, P; Wilson-Hodge, C A

2013-01-01T23:59:59.000Z

258

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

E-Print Network (OSTI)

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...

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; Carramiñana, 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; Villaseñor, 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

259

Particle Acceleration and Gamma-Ray Production in Shell Remnants  

E-Print Network (OSTI)

A number of nearby Northern Hemisphere shell-type Supernova Remnants (SNRs) has been observed in TeV gamma rays, but none of them could be detected so far. This failure calls for a critical reevaluation of the theoretical arguments for gamma-ray emission of SNRs. The present paper discusses diffusive shock acceleration in shell-type SNRs in full kinetic theory. Emphasis is also given to the possible problems for VHE gamma-ray production due to the environmental conditions a SN progenitor finds itself in. Observational upper limits are compared with theoretical predictions for the gamma-ray flux. Empirical arguments from the observation of X-ray power law continua for electron-induced Inverse Compton gamma-ray emission at TeV energies are discussed in their relation to the nucleonic Pi-zero decay emission from the same objects. Finally, a point is made for the simplest case of SNe Ia, expected to explode in a uniform circumstellar medium. Here in particular the very recently detected Southern Hemisphere remnant of SN 1006 is compared with Tycho's SNR. On the basis of the assumed parameters for the two remnants SN 1006 is tentatively identified with a remnant whose TeV gamma-ray emission is dominated by Inverse Compton radiation. Tycho might be dominantly a Pi-zero decay gamma-ray source.

H. J. Volk

1997-11-18T23:59:59.000Z

260

A Gamma-Ray Burst Trigger Toolkit  

E-Print Network (OSTI)

The detection rate of a gamma-ray burst detector can be increased by using a count rate trigger with many accumulation times ?t and energy bands ?E. Because a burst’s peak flux varies when averaged over different ?t and ?E, the nominal sensitivity (the numerical value of the peak flux) of a trigger system is less important than how much fainter a burst could be at the detection threshold as ?t and ?E are changed. The relative sensitivity of different triggers can be quantified by referencing the detection threshold back to the peak flux for a fiducial value of ?t and ?E. This mapping between peak flux values for different sets of ?t and ?E varies from burst to burst. Quantitative estimates of the burst detection rate for a given detector and trigger system can be based on the observed rate at a measured peak flux value in this fiducial trigger. Predictions of a proposed trigger’s burst detection rate depend on the assumed burst population, and these predictions can be wildly in error for triggers that differ significantly from previous missions. I base the fiducial rate on the BATSE observations: 550 bursts per sky above a peak flux of 0.3 ph cm ?2 s ?1 averaged over ?t=1.024 s and ?E=50–300 keV. Using a sample of 100 burst lightcurves I find that triggering on all possible values of ?t that are multiples of 0.064 s decreases the average threshold peak flux on the 1.024 s timescale by a factor of 0.6. Extending ?E to lower energies includes the large flux of the X-ray background, increasing the background count rate. Consequently a low energy ?E is advantageous only for very soft bursts. Whether a large fraction of the population of bright bursts is soft is disputed; the new population of X-ray Flashes is soft but relatively faint. Subject headings: gamma-rays: bursts

unknown authors

2002-01-01T23:59:59.000Z

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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Gamma Ray Burst Constraints on Ultraviolet Lorentz Invariance Violation  

E-Print Network (OSTI)

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).

Tina Kahniashvili; Grigol Gogoberidze; Bharat Ratra

2006-07-04T23:59:59.000Z

262

1 UNIDENTIFIED GAMMA-RAY SOURCES AND MICROQUASARS  

E-Print Network (OSTI)

Some phenomenological properties of the unidentified EGRET detections suggest that there are two distinct groups of galactic gamma-ray sources that might be associated with compact objects endowed with relativistic jets. We discuss different models for gamma-ray production in both microquasars with low- and high-mass stellar companions. We conclude that the parent population of low-latitude and halo variable sources might be formed by yet undetected microquasars and microblazars. Key words: Gamma ray sources: unidentified; microquasars; black holes. 1.

G. E. Romero; I. A Grenier; M. M. Kaufman Bernadó; I. F. Mirabel; D. F. Torres

2004-01-01T23:59:59.000Z

263

of Bright, Long Gamma-Ray Bursts  

E-Print Network (OSTI)

The time profiles of many gamma-ray bursts observed by BATSE consist of distinct pulses, which offer the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse-shape parameters. This pulse analysis has previously been performed on some bright, long bursts using binned data, and on some short bursts using BATSE Time-Tagged Event (TTE) data. The BATSE Time-to-Spill (TTS) burst data records the times required to accumulate a fixed number of photons, giving variable time resolution. The spill times recorded in the TTS data behave as a gamma distribution. We have developed an interactive pulse-fitting program using the pulse model of Norris et al. and a maximum-likelihood fitting algorithm to the gamma distribution of the spill times. We then used this program to analyze a number of bright, long bursts for which TTS data is available. We present statistical information on the attributes of pulses comprising these bursts.

Andrew Lee; Elliott Bloom; Jeffrey Scargle

1996-01-01T23:59:59.000Z

264

The gamma-ray burst GB 920622  

E-Print Network (OSTI)

We have analyzed the Ulysses, BATSE, and COMPTEL spectral data from the \\gamma-ray burst of June 22, 1992 (GB 920622). COMPTEL data reveal a hard to soft evolution within the first pulse of the burst, while the mean hardness ratios of the three pulses are the same. Unlike the single instrument spectra, the composite spectrum of GB 920622 averaged over the total burst duration ranging from 20 keV up to 10 MeV cannot be fit by a single power law. Instead, the spectrum shows continuous curvature across the full energy range. COMPTEL imaging and BATSE/Ulysses triangulation constrain the source location of GB 920622 to a ring sector 1.1 arcmin wide and 2 degrees long. This area has been searched for quiescent X-ray sources using \\ros survey data collected about two years before the burst. After the optical identification of the X-ray sources in and near the GRB location we conclude that no quiescent X-ray counterpart candidate for GB 920622 has been found.

Greiner, J; Bade, N; Fishman, G J; Hanlon, L O; Hurley, K; Kippen, R M; Kouveliotou, C; Preece, R D; Ryan, J; Schönfelder, V; Williams, O R; Winkler, C M; Boër, M; Niel, M

1995-01-01T23:59:59.000Z

265

A Theory of Gamma-Ray Bursts  

E-Print Network (OSTI)

We present a specific scenario for the link between GRB and hypernovae, based on Blandford-Znajek extraction of black-hole spin energy. Such a mechanism requires a high angular momentum in the progenitor object. The observed association of gamma-ray bursts with type Ibc supernovae leads us to consider massive helium stars that form black holes at the end of their lives as progenitors. We combine the numerical work of MacFadyen & Woosley with analytic calculations, to show that about 1E53 erg each are available to drive the fast GRB ejecta and the supernova. The GRB ejecta are driven by the power output through the open field lines, whereas the supernova is powered by closed filed lines and jet shocks. We also present a much simplified approximate derivation of these energetics. Helium stars that leave massive black-hole remnants in special ways, namely via soft X-ray transients or very massive WNL stars. Since binaries naturally have high angular momentum, we propose a link between black-hole transients a...

Brown, G E; Wijers, R A M J; Lee, H K; Israelian, G; Bethe, Hans Albrecht

2000-01-01T23:59:59.000Z

266

Robust Limits on Lorentz Violation from Gamma-Ray Bursts  

E-Print Network (OSTI)

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.

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

2005-10-06T23:59:59.000Z

267

A Gamma-Ray Burst Bibliography, 1973-1999  

E-Print Network (OSTI)

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.

K. Hurley

1999-12-02T23:59:59.000Z

268

Observations of Gamma-Ray Bursts at Extreme Energies.  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs), thought to be produced by the core-collapse of massive stars or merging compact objects, are the most luminous events observed since the… (more)

Aune, Taylor

2012-01-01T23:59:59.000Z

269

In-beam gamma-ray spectroscopy of target fragmentation  

E-Print Network (OSTI)

E ? - E ? correlation matrix which contained the energy anddata into a 2D matrix of gamma-ray energy of clean Ge hitsenergy (belonging to a specific nucleus), we projected the matrix

2004-01-01T23:59:59.000Z

270

Redshifts of the Long Gamma-Ray Bursts  

E-Print Network (OSTI)

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.

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

2007-04-06T23:59:59.000Z

271

The Optical Afterglows of Gamma-Ray Bursts  

E-Print Network (OSTI)

The optical afterglows of gamma-ray bursts can be used to probe the physics, geometry, and environments of gamma-ray bursts. In this article I discuss the how spectra and photometry can be used to constrain fireball parameters, describe several types of breaks that might be observed in the optical decay, and briefly review the late-time bumps and rapid variations in optical light curves.

S. T. Holland

2002-11-18T23:59:59.000Z

272

Hyperstars - Main Origin of Short Gamma Ray Bursts?  

E-Print Network (OSTI)

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.

Arnon Dar

2005-09-09T23:59:59.000Z

273

Gamma Ray Bursts as Probes of Quantum Gravity  

E-Print Network (OSTI)

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.

Tsvi Piran

2004-07-21T23:59:59.000Z

274

Relativity at Action or Gamma-Ray Bursts  

E-Print Network (OSTI)

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.

Tsvi Piran

1996-07-08T23:59:59.000Z

275

HETEROGENEITY IN SHORT GAMMA-RAY BURSTS  

SciTech Connect

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.

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

276

Gamma Ray Bursts as seen by a Giant Air Shower Array  

E-Print Network (OSTI)

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.

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

1997-12-19T23:59:59.000Z

277

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

E-Print Network (OSTI)

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

California at Santa Cruz, University of

278

Ivan De Mitri VHE Gamma Ray Astronomy 1 Very High Energy  

E-Print Network (OSTI)

~ 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

Harrison, Thomas

279

PoGO : The Polarised Gamma-ray Observer S. Larssona  

E-Print Network (OSTI)

. 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

Haviland, David

280

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

E-Print Network (OSTI)

. 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

Cummer, Steven A.

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

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

E-Print Network (OSTI)

, 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

California at Santa Cruz, University of

282

THE NEW CANGAROO TELESCOPE AND THE PROSPECT OF VHE GAMMA RAY OBSERVATION AT  

E-Print Network (OSTI)

GammaWhat about Gamma--Ray Bursts?Ray Bursts? Extremely powerful explosions happen in galaxies The Quest for Gamma Rays:The Quest for Gamma Rays: Exploring the Most Violent PlacesExploring the Most is gammaWhat is gamma--ray background light like?ray background light like? How diffuse is the gamma

Enomoto, Ryoji

283

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

E-Print Network (OSTI)

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

California at Santa Cruz, University of

284

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

E-Print Network (OSTI)

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

Zhang, Bing

285

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

Science Conference Proceedings (OSTI)

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.

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

286

(DOI: will be inserted by hand later) Light Curves of Swift Gamma Ray Bursts  

E-Print Network (OSTI)

Abstract. Recent observations from the Swift gamma ray burst explorer indicate that a large 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 gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars. Key words. gamma-rays: bursts 1.

Paolo Cea

2006-01-01T23:59:59.000Z

287

Fermi LAT Observations of LS 5039  

SciTech Connect

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.

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

288

Testing Gamma-Ray Burst Jet Structure with the Distribution of Gamma-Ray Energy Release  

E-Print Network (OSTI)

We present a general method for testing gamma-ray burst (GRB) jet structure and carry out a comprehensive analysis about the prevalent jet structure models. According to the jet angular energy distribution, we can not only derive the expected distribution of the GRB isotropic-equivalent energy release for any possible jet structure, but also obtain a two-dimensional distribution including redshift z. By using the Kolmogorov-Smirnov test we compare the predicted distribution with the observed sample, and find that the power-law structured jet model is most consistent with the current sample and that the uniform jet model is also plausible. However, this conclusion is tentative because of the small size and the inhomogeneity of this sample. Future observations (e.g., Swift) will provide a larger and less biased sample for us to make a robust conclusion by using the procedure proposed in this paper.

L. Xu; X. F. Wu; Z. G. Dai

2005-08-15T23:59:59.000Z

289

VHE gamma-ray emission from the FSRQs observed by the MAGIC telescopes  

E-Print Network (OSTI)

Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs): PKS 1510-089, PKS 1222+216 and 3C 279. The detection of FSRQs in the VHE range is challenging, mainly because of their steep soft spectra in the GeV-TeV regime. MAGIC has observed and detected all FSRQs known to be VHE emitters up to now and found that they exhibit very different behavior. The 2010 discovery of PKS 1222+216 (z = 0.432) with the fast variability observed, challenges simple one-zone emission models and more complicated scenarios have been proposed. 3C 279 is the most distant VHE gamma-ray emitting AGN (z = 0.536), which was discovered by MAGIC in 2006 and detected again in 2007. In 2011 MAGIC observed 3C 279 two times: first during a monitoring campaign and later observations were triggered by a flare detected with Fermi-LAT. We present the MAGIC results and the multiwavelength behavior during this flaring epoch. Finally, we report the ...

Lindfors, E; de Almeida, U Barres; Mazin, D; Paneque, D; Saito, K; Gonzalez, J Becerra; Berger, K; De Caneva, G; Schultz, C; Sitarek, J; Stamerra, A; Tavecchio, F; Buson, S; D'Ammando, F; Hayashida, M; Tornikoski, M; Hovatta, T

2013-01-01T23:59:59.000Z

290

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

Science Conference Proceedings (OSTI)

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.

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

291

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

E-Print Network (OSTI)

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.

Philipp Baerwald; Mauricio Bustamante; Walter Winter

2014-01-08T23:59:59.000Z

292

Gamma-Ray Bursts from Radio-Quiet Quasars  

E-Print Network (OSTI)

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).

N. Schartel; H. Andernach; J. Greiner

1996-12-16T23:59:59.000Z

293

On the nature of gamma-ray burst time dilations  

E-Print Network (OSTI)

The recent discovery that faint gamma-ray bursts are stretched in time relative to bright ones has been interpreted as support for cosmological distances: faint bursts have their durations redshifted relative to bright ones. It was pointed out, however, that the relative time stretching can also be produced by an intrinsic correlation between duration and luminosity of gamma-ray bursts in a nearby, bounded distribution. While both models can explain the average amount of time stretching, we find a difference between them in the way the duration distribution of faint bursts deviates from that of bright ones, assuming the luminosity function of gamma-ray bursts is independent of distance. This allows us to distinguish between these two broad classes of model on the basis of the duration distributions of gamma-ray bursts, leading perhaps to an unambiguous determination of the distance scale of gamma-ray bursts. We apply our proposed test to the second BATSE catalog and conclude, with some caution, that the data favor a cosmological interpretation of the time dilation.

Ralph A. M. J. Wijers; Bohdan Paczy?ski

1994-08-02T23:59:59.000Z

294

Diffuse gamma-ray emission: Galactic and extragalactic  

E-Print Network (OSTI)

Here is reviewed our current understanding of Galactic and extragalactic diffuse gamma-ray emission. The spectrum of the extragalactic gamma-ray background above 30 MeV can be well described by a power law with photon index s=2.1. In the 2-10 MeV range a preliminary analysis of COMPTEL data indicates a lower intensity than previously found, with no evidence for an MeV bump. Most of the models of a truly diffuse background seem to be in conflict with the observed spectrum. Though AGN are the most likely input from discrete sources, two independent attempts to model the high energy background as the superposition of unresolved AGN indicate that AGN underproduce the observed intensity. Therefore the origin of the extragalactic gamma-ray background is still unknown. The Galactic diffuse gamma-ray continuum is more intense than expected both at very low energies (energies (> 1 GeV). The published models for these excesses all involve cosmic ray electron interactions. While the low energy excess may have something to do with in-situ acceleration of electrons, the excess at high energies may be understood if the sources of cosmic ray electrons are discrete. The measured energy spectrum of the diffuse Galactic gamma-ray continuum radiation thus may provide new insights into the acceleration of cosmic rays.

Martin Pohl

1998-07-27T23:59:59.000Z

295

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

E-Print Network (OSTI)

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.

Kunihito Ioka

2008-12-30T23:59:59.000Z

296

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

E-Print Network (OSTI)

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.

Péter Mészáros; Katsuaki Asano; Péter Veres

2012-09-11T23:59:59.000Z

297

Gamma-Ray Bursts and Topology of the Universe  

E-Print Network (OSTI)

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.

Marek Biesiada

1993-10-04T23:59:59.000Z

298

Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification  

SciTech Connect

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.

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

2012-11-01T23:59:59.000Z

299

AGN models for the X and gamma-ray backgrounds  

E-Print Network (OSTI)

The origin of the X-ray background spectral intensity has been a long standing problem in high energy astrophysics research. Deep X-ray surveys carried out with ROSAT and ASCA combined with the broad band spectral results of Ginga and BeppoSAX satellites strongly support the hypothesis that the bulk of the X-ray background is due to the integrated contribution of discrete sources (mainly AGNs). At higher energies the unexpected findings of the Compton Gamma Ray Observatory indicate that also the gamma-ray background is likely to be due to AGNs. I will discuss AGN--based models for the high energy backgrounds and how future observations will improve our understanding of the X and gamma-ray backgrounds and of the physics and evolution of AGNs.

Andrea Comastri

1998-12-16T23:59:59.000Z

300

Gamma-ray Pulsars in a Modified Polar Cap Scenario  

E-Print Network (OSTI)

We present a polar-cap model which incorporates a likely acceleration of Sturrock pairs with their subsequent contribution to gamma-ray luminosity L_gamma. This model reproduces L_gamma for seven pulsars detected with Compton Gamma Ray Observatory experiments, avoiding at the same time the problem of the empirical gamma-ray death line of Arons (1996). Also, we estimate the efficiency of reversing newly created positrons by residual longitudinal electric field. Over the wide range of spin-down luminosity values the predicted polar-cap X-ray luminosity L_X(pc) goes as L_sd^{0.6}. Model calculations for B0823+26, B0950+08, B1929+10, and J0437-4715 are compared with existing observational constraints on thermal X-ray components.

B. Rudak; J. Dyks

1997-10-22T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
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301

Gamma-ray spectrometer utilizing xenon at high pressure  

SciTech Connect

A prototype gamma-ray spectrometer utilizing xenon gas near the critical point (166{degrees}C, 58 atm) is under development. The spectrometer will function as a room-temperature ionization chamber detecting gamma rays in the energy range 100 keV2 MeV, with an energy resolution intermediate between semiconductor (Ge) and scintillation (NaI) spectrometers. The energy resolution is superior to that of a NaI scintillation spectrometer by a substantial margin (approximately a factor 5), and accordingly, much more information can be extracted from a given gamma-ray spectrum. Unlike germanium detectors, the spectrometer possesses the capability for sustained operation under ambient temperature conditions without a requirement for liquid nitrogen.

Smith, G.C.; Mahler, G.J.; Yu, B.; Kane, W.R. [Brookhaven National Lab., Upton, NY (United States); Markey, J.K. [Yale Univ., New Haven, CT (United States). School of Medicine

1994-08-01T23:59:59.000Z

302

High Energy Gamma Rays from Protons Hitting Compact Objects  

E-Print Network (OSTI)

In a previous paper the spectrum of positrons produced by matter initially at rest falling onto a massive compact object was calculated. In this paper this calculation is generalized to obtain both the spectrum of in-flight positron annihilation and pi0 decay gamma rays produced when protons with a cosmic ray-like spectrum hit the surface. The resulting pi0 decay gamma ray spectrum reflects the high energy proton energy spectrum, and is largely independent of the mass of the compact object. One notable prediction for all compact objects is a dip in the spectrum below 70 MeV. As applied to the 10^6 solar mass massive compact object near to the center of our galaxy, our theory shows promise for explaining the gamma rays coming from the galactic center as observed by both the Compton satellite and HESS ground based array.

J. Barbieri; G. Chapline

2008-06-09T23:59:59.000Z

303

Pulser injection with subsequent removal for gamma-ray spectrometry  

DOE Patents (OSTI)

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 figs.

Hartwell, J.K.; Goodwin, S.G.; Johnson, L.O.; Killian, E.W.

1989-02-01T23:59:59.000Z

304

Are Durations of Weak Gamma-Ray Bursts Reliable?  

E-Print Network (OSTI)

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 listed in the BATSE catalog would be useful in quantifying the effect. PACS 95.85.Pw – gamma-ray. PACS 98.70.Rz – gamma-ray bursts.

Maarten Schmidt

2005-01-01T23:59:59.000Z

305

Diffuse Gamma-Rays from Local Group Galaxies  

E-Print Network (OSTI)

Diffuse gamma-ray radiation in galaxies is produced by cosmic ray interactions with the interstellar medium. With the completion of EGRET observations, the only extragalactic object from which there has been a positive detection of diffuse gamma-ray emission is the Large Magellanic Cloud. We systematically estimate the expected diffuse gamma-ray flux from Local Group galaxies, and determine their detectability by new generation gamma-ray observatories such as GLAST. For each galaxy, the expected gamma-ray flux depends only on its total gas content and its cosmic ray flux. We present a method for calculating cosmic ray flux in these galaxies in terms of the observed rate of supernova explosions, where cosmic ray acceleration is believed to take place. The difficulty in deriving accurate supernova rates from observational data is a dominant uncertainty in our calculations. We estimate the gamma-ray flux for Local Group galaxies and find that our predictions are consistent with the observations for the LMC and with the observational upper limits for the Small Magellanic Cloud and M31. Both the Andromeda galaxy, with a flux of $\\sim 1.0 \\times 10^{-8}$ photons sec$^{-1}$ cm$^{-2}$ above 100 MeV, and the SMC, with a flux of $\\sim 1.7 \\times 10^{-8}$ photons sec$^{-1}$ cm$^{-2}$ above 100 MeV, are expected to be observable by GLAST. M33 is at the limit of detectability with a flux of $\\sim 0.11 \\times 10^{-8}$ sec$^{-1}$ cm$^{-2}$. Other Local Group galaxies are at least two orders of magnitude below GLAST sensitivity.

Vasiliki Pavlidou; Brian D. Fields

2001-05-11T23:59:59.000Z

306

X-ray afterglows from gamma-ray bursts  

E-Print Network (OSTI)

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.

M. Tavani

1997-03-24T23:59:59.000Z

307

Present and future gamma-ray burst experiments  

E-Print Network (OSTI)

Gamma-ray burst counterpart studies require small, prompt error boxes. Today, there are several missions which can provide them: BeppoSAX, the Rossi X-Ray Timing Explorer, and the 3rd Interplanetary Network. In the near future, HETE-II, a possible extended Interplanetary Network, and INTEGRAL will operate in this capacity. In the longer term future, a dedicated gamma-ray burst MIDEX mission may fly. The capabilities of these missions are reviewed, comparing the number of bursts, the rapidity of the localizations, and the error box sizes.

K. Hurley

1998-12-21T23:59:59.000Z

308

A Gamma-Ray Bursts' Fluence-Duration Correlation  

E-Print Network (OSTI)

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.

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

2005-08-01T23:59:59.000Z

309

Correlation between Gamma-Ray bursts and Gravitational Waves  

E-Print Network (OSTI)

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.

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

310

A celestial gamma-ray foreground due to the albedo of small solar system bodies and a remote probe of the interstellar cosmic ray spectrum  

E-Print Network (OSTI)

We calculate the gamma-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids (MBAs), Jovian and Neptunian Trojan asteroids, and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the gamma-ray albedo for the Main Belt, Trojans, and Kuiper Belt strongly depends on the small-body size distribution of each system. Based on an analysis of the Energetic Gamma Ray Experiment Telescope (EGRET) data we infer that the diffuse emission from the MBAs, Trojans, and KBOs has an integrated flux of less than ~6x10^{-6} cm^{-2} s^{-1} (100-500 MeV), which corresponds to ~12 times the Lunar albedo, and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). If detected by GLAST, it can provide unique direct information about the number of small bodies in each system that is difficult to assess by any other method. Additionally, the KBO albedo flux can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions. The orbits of MBAs, Trojans, and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. Therefore, the asteroid gamma-ray albedo has to be taken into account when analyzing weak gamma-ray sources close to the ecliptic, especially near the Galactic center and for signals at high Galactic latitudes, such as the extragalactic gamma-ray emission. 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.

Igor V. Moskalenko; Troy A. Porter; Seth W. Digel; Peter F. Michelson; Jonathan F. Ormes

2007-12-12T23:59:59.000Z

311

THE INTERNAL-COLLISION-INDUCED MAGNETIC RECONNECTION AND TURBULENCE (ICMART) MODEL OF GAMMA-RAY BURSTS  

Science Conference Proceedings (OSTI)

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests that the central engine likely launches a Poynting-flux-dominated (PFD) outflow. We propose a model of gamma-ray burst (GRB) prompt emission in the PFD 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 (e.g., 1 {approx}lines entrained in the ejecta. 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 distorts field lines easing additional magnetic reconnections, resulting in a runway release of the stored magnetic field energy (an ICMART event). Particles are accelerated either directly in the reconnection zone, or stochastically in the turbulent regions, which radiate synchrotron photons that power the observed gamma rays. Each ICMART event corresponds to a broad pulse in the GRB light curve, and a GRB is composed of multiple ICMART events. This model retains the merits of IS and other models, but may overcome several difficulties/issues faced by the IS model (e.g., low efficiency, fast cooling, electron number excess, Amati/Yonetoku relation inconsistency, and missing bright photosphere). Within this model, the observed GRB variability timescales could have two components, one slow component associated with the central engine time history, and another fast component associated with relativistic magnetic turbulence in the emission region. The model predicts a decrease of gamma-ray polarization degree and E{sub p} in each ICMART event (broad pulse) during the prompt GRB phase, as well as a moderately magnetized external reverse shock. The model may be applied to the GRBs that have time-resolved, featureless Band-function spectra, such as GRB 080916C and most GRBs detected by Fermi LAT.

Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Yan Huirong [Kavli Institute of Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

2011-01-10T23:59:59.000Z

312

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

Science Conference Proceedings (OSTI)

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 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.

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

313

X-ray Spectral Properties of Gamma-Ray Bursts  

E-Print Network (OSTI)

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%.

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

1997-12-18T23:59:59.000Z

314

A Gamma-Ray Burst Bibliography, 1973-2001  

E-Print Network (OSTI)

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.

K. Hurley

2002-01-18T23:59:59.000Z

315

Gamma Ray Bursts as Probes of the First Stars  

E-Print Network (OSTI)

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.

James E. Rhoads

2001-11-01T23:59:59.000Z

316

The Pionic Contribution to Diffuse Gamma Rays: Upper Limits  

E-Print Network (OSTI)

Diffuse gamma rays probe the highest-energy processes at the largest scales. Here we derive model-independent constraints on the hadronic contribution to the Galactic and extragalactic gamma-ray spectra in the energy range 50 MeV < E_gamma < 10 GeV. The hadronic component is dominated by emission from neutral pions, with a characteristic spectrum symmetric about m_{pi^0}/2. We exploit the well-defined properties of the pion decay spectrum to quantify the maximum pionic fraction of the observed gamma-ray intensity. We find that the Galactic spectrum above 30 MeV can be at most about 50% pionic. The maximum pionic contribution to the extragalactic spectrum is energy dependent; it also depends on the redshift range over which the sources are distributed, ranging from as low as about 20% for pions generated very recently, to as much as 90% if the pions are generated around redshift 10. The implications of these constraints for models of gamma-ray and neutrino emission are briefly discussed.

Tijana Prodanovic; Brian D. Fields

2004-03-12T23:59:59.000Z

317

Cosmic Rays and Gamma Ray Bursts From Microblazars  

E-Print Network (OSTI)

Highly relativistic jets from merger and accretion induced collapse of compact stellar objects, which may produce the cosmological gamma ray bursts (GRBs), are also very efficient and powerful cosmic ray accelerators. The expected luminosity, energy spectrum and chemical composition of cosmic rays from Galactic GRBs, most of which do not point in our direction, can explain the observed properties of Galactic cosmic rays.

Arnon Dar

1998-09-13T23:59:59.000Z

318

Afterglows as Diagnostics of Gamma Ray Burst Beaming  

E-Print Network (OSTI)

Abstract. 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 (?> ? 100) inferred from GRB spectra imply relativistic beaming of the gamma rays into an angle ? 1/?. 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 ?m undergoes a qualitative change in evolution when ??m < ? 1: Before this, ? ? r?3/2, while afterwards, ? ? exp(?r/r ?

James E. Rhoads

1997-01-01T23:59:59.000Z

319

Neutrino production in nucleonic interactions in gamma-ray bursters  

E-Print Network (OSTI)

Neutrinos produced in gamma-ray bursters (GRBers) may provide a unique probe for the physics of these extreme astrophysical systems. Here we discuss neutrino production in inelastic neutron-proton collisions within the relativistic outflows associated with GRBers. We consider both the widely used fireball model and a recently proposed magneto-hydrodynamic (MHD) model for the GRB outflow.

Hylke B. J. Koers

2008-05-16T23:59:59.000Z

320

Can Fireball or Firecone Models Explain Gamma Ray Bursts?  

E-Print Network (OSTI)

The observed afterglows of gamma ray bursts, in particular that of GRB 970228 six months later, seem to rule out relativistic fireballs and relativistic firecones driven by merger or accretion induced collapse of compact stellar objects in galaxies as the origin of GRBs. GRBs can be produced by superluminal jets from such events.

Arnon Dar

1997-09-24T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

The efficiency of gamma-ray emission from pulsars  

E-Print Network (OSTI)

We present a modified scenario of gamma-ray emission from pulsars within the framework of polar cap models. Our model incorporates possible acceleration of electron-positron pairs created in magnetospheres, and their subsequent contribution to gamma-ray luminosity L_\\gamma. It also reproduces the empirical trend in L_\\gamma for seven pulsars detected with Compton Gamma Ray Observatory (CGRO) experiments. At the same time it avoids basic difficulties (Nel et al. 1996, Arons 1996) faced by theoretical models when confronted with observational constraints. We show that the classical and millisecond pulsars form two distinct branches in the L_gamma - L_sd diagram (where L_sd is the spin-down luminosity). In particular, we explain why the millisecond pulsar J0437-4715 has not been detected with any of the CGRO instruments despite its very high position in the ranking list of spin-down fluxes (i.e. L_sd/D^2, where D is a distance). The gamma-ray luminosity predicted for this particular object is about one order of magnitude below the upper limit set by EGRET.

B. Rudak; J. Dyks

1997-10-22T23:59:59.000Z

322

Gamma-Ray Exposure Rate Distribution in a Steam Generator  

Science Conference Proceedings (OSTI)

Gamma-ray exposure rate measurements were made with thermoluminescent dosimeters to determine the relative contribution of various surface areas in a steam generator to the overall radiation levels. The measurements were compared with analytic predictions based on discrete ordinates and point kernel techniques, and assessments of the radiation source inventory of the various surfaces were developed.

1983-05-01T23:59:59.000Z

323

Constraints on relativity violations from gamma-ray bursts  

E-Print Network (OSTI)

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.

Alan Kostelecky; Matthew Mewes

2013-01-23T23:59:59.000Z

324

Are there cosmological evolution of Gamma-Ray Bursts?  

E-Print Network (OSTI)

The variability of gamma-ray burst (GRB) is thought to be correlated with its absolute peak luminosity, and this relation had been used to derive an estimate of the redshifts of GRBs. Recently Amati et al. present the results of spectral and energetic properties of several GRBs with know redshifts. Here we analyse the properties of two group GRBs, one group with known redshift from afterglow observation, and another group with redshift derived from the luminosity- variability relation. We study the redshift dependence of various GRBs features in their cosmological rest frames, including the burst duration, the isotropic luminosity and radiated energy, and the peak energy Ep of ?F? spectra. We find that the properties of these two group GRBs are very similar, which strongly implies that the redshift derived from the luminosity-variability relation may be reliable. If this is true, then we see that the burst properties, such as their intrinsic duration, luminosity, radiated energy and peak energy Ep, are all correlated with the redshift, which means that the GRBs features are redshift dependent, i.e. there are cosmological evolution of gamma-ray bursts, and this can provide an interesting clue to the nature of GRBs. Furthermore we find that the Ep- L relation strongly supports the idea that gamma-ray burst emission comes from the internal shock. Key words: gamma rays: bursts

D. M. Wei

2008-01-01T23:59:59.000Z

325

Gamma-ray Bursts and their Central Engines  

E-Print Network (OSTI)

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.

Stephan Rosswog

2004-01-04T23:59:59.000Z

326

Constraining axion by polarized prompt emission from gamma ray bursts  

E-Print Network (OSTI)

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.

A. Rubbia; A. S. Sakharov

2007-08-20T23:59:59.000Z

327

Plutonium Isotopic Measurements by Gamma-Ray Spectroscopy  

SciTech Connect

The nondestructive assay of plutonium is important as a safeguard tool in accounting for stategic nuclear material. Several nondestructive assay techniques, e.g., calorimetry and spontaneous fission assay detectors, require a knowledge of plutonium and americium isotopic ratios to convert their raw data to total grams of plutonium. This paper describes a nondestructive technique for calculating plutonium-238, plutonium-240, plutonium-241 and americium-241 relative to plutonium-239 from measured peak areas in the high resolution gamma-ray spectra of solid plutonium samples. Gamma-ray attenuation effects have been minimized by selecting sets of neighboring peaks in the spectrum whose components are due to the different isotopes. Since the detector efficiencies are approximately the same for adjacent peaks, the accuracy of the isotopic ratios are dependent on the half-lives, branching intensities and measured peak areas. The data presented describes the results obtained by analyzing gamma-ray spectra in the energy region from 120 to 700 keV. The majority of the data analyzed was obtained from plutonium material containing 6% plutonium-240. Sample weights varied from 0.25 g to approximately 1.2 kg. The methods have also been applied to plutonium samples containing up to 23% plutonium-240 with weights of 0.25 to 200g. Results obtained by gamma-ray spectroscopy are compared to chemical analyses of aliquots taken from the bulk samples.

Haas, Francis X.; Lemming, John F.

1976-05-01T23:59:59.000Z

328

Current Trends in Gamma Ray Detection for Radiological Emergency Response  

SciTech Connect

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.

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

2011-08-18T23:59:59.000Z

329

High-energy emission and recent afterglow studies of gamma-ray bursts.  

E-Print Network (OSTI)

??Gamma-ray Bursts (GRBs) are powerful explosions that emit most of their energy, as their name suggests, in gamma-rays of typical energies of about 1 MeV.… (more)

Barniol Duran, Rodolfo Jose

2011-01-01T23:59:59.000Z

330

A Multi-wavelength study on gamma-ray bursts and their afterglows.  

E-Print Network (OSTI)

??During the prompt emission and afterglow phases, GRBs(Gamma-Ray Bursts) release their huge amount of energy not limited in gamma-ray, but in a wide range of… (more)

Zhang, Binbin

2011-01-01T23:59:59.000Z

331

Highlights of the Rome Workshop on Gamma-Ray Bursts in the Afterglow Era  

E-Print Network (OSTI)

I review some of the highlights of the Rome Workshop on Gamma-Ray Bursts, and discuss some of the questions these results pose about the nature and origin of gamma-ray bursts.

D. Q. Lamb

1999-09-01T23:59:59.000Z

332

Total-to-peak ratios of high purity germanium gamma ray detector  

E-Print Network (OSTI)

This study is concerned with the percentage of [gamma]-rays of a certain energy having their energy correctly measured by a high purity Germanium [gamma]-ray detector. The ratio between the total counts and the counts ...

Nelson, Justin Matthew, 1981-

2004-01-01T23:59:59.000Z

333

Relativistic Winds from Compact Gamma-Ray Sources: II. Pair Loading and Radiative Acceleration in Gamma-ray Bursts  

E-Print Network (OSTI)

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.

Christopher Thompson; Piero Madau

1999-09-06T23:59:59.000Z

334

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

E-Print Network (OSTI)

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

California at Santa Cruz, University of

335

Six Years of Gamma Ray Burst Observations with BeppoSAX  

E-Print Network (OSTI)

I give a summary of the prompt X-/gamma-ray detections of Gamma Ray Bursts (GRBs) with the BeppoSAX satellite and discuss some significant results obtained from the study of the prompt emission of these GRBs obtained with the BeppoSAX Gamma Ray Burst Monitor and Wide Field Cameras.

Filippo Frontera

2004-07-30T23:59:59.000Z

336

Search for Short Duration Bursts of TeV Gamma Rays with the Milagrito Telescope  

E-Print Network (OSTI)

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

California at Santa Cruz, University of

337

arXiv:astro-ph/0509571v119Sep2005 Gamma-Ray Burst Early Afterglows  

E-Print Network (OSTI)

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

Zhang, Bing

338

Gamma-Ray Bursts in the Swift Era N. Gehrels,1  

E-Print Network (OSTI)

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

Rodriguez, Luis F.

339

The Interplanetary Network Supplement to the BATSE 5B Catalog of Cosmic Gamma-Ray Bursts  

E-Print Network (OSTI)

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

California at Berkeley, University of

340

Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts  

E-Print Network (OSTI)

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

California at Berkeley, University of

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

THE INTERPLANETARY NETWORK SUPPLEMENT TO THE BATSE CATALOGS OF UNTRIGGERED COSMIC GAMMA-RAY BURSTS  

E-Print Network (OSTI)

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

California at Berkeley, University of

342

Vol. 35 (2004) ACTA PHYSICA POLONICA B No 6--7 GAMMA RAY BURSTS #  

E-Print Network (OSTI)

multiwavelength survey of 63 Gamma Ray Bursts (GRBs) with unprecedented temporal coverage, we classify. Keywords: gamma-ray sources; gamma-ray bursts PACS: 98.70.Rz INTRODUCTION Using the network of three 2-m in our sample. Right panel : X-ray vs. optical flux (extrapolated at t=10 minutes after the burst event

Magiera, Andrzej

343

A ground level gamma-ray burst observed in association with rocket-triggered lightning  

E-Print Network (OSTI)

ray bursts which BeppoSAX satellite detected with one arcminute accuracy. 3 VHE GAMMA RAY EMISSION 1111111111111111111111111111111111111111111111111111111111111111111111111111111111111 (d) 30 20 10 0 -10 1051520 ActiveGalacticNuclei Log(Sizer(cm)) SuperNova Explosion GammaRayBurst@icrr.u-tokyo.ac.jp ABSTRACT Copious production of electrons and positrons results in very high energy gamma-rays from

Slatton, Clint

344

MilagroA TeV Observatory for Gamma Ray Bursts  

E-Print Network (OSTI)

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

California at Santa Cruz, University of

345

The short gamma-ray burst SGR giant flare connection Kevin Hurley  

E-Print Network (OSTI)

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

California at Berkeley, University of

346

Limits on Very High Energy Emission from Gamma-Ray Bursts with the Milagro  

E-Print Network (OSTI)

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

California at Santa Cruz, University of

347

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-8493-0052-5/00/$0.00+$.50 c 2001 by CRC Press LLC 5 #12;#12;Chapter 1 Cactus Framework: Black Holes to Gamma Ray Bursts Erik

348

GAMMA-RAY BURSTS AND THE EARTH: EXPLORATION OF ATMOSPHERIC, BIOLOGICAL, CLIMATIC, AND BIOGEOCHEMICAL EFFECTS  

E-Print Network (OSTI)

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

Jackman, Charles H.

349

SOLAR SUBMILLIMETER AND GAMMA-RAY BURST EMISSION P. Kaufmann,1,2  

E-Print Network (OSTI)

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

Giménez de Castro, Guillermo Carlos

350

UNIVERSITY of CALIFORNIA A SEARCH FOR TEV GAMMA-RAY BURST EMISSION WITH  

E-Print Network (OSTI)

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

California at Santa Cruz, University of

351

Climatic and biogeochemical effects of a galactic gamma ray burst Adrian L. Melott,1  

E-Print Network (OSTI)

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

Jackman, Charles H.

352

arXiv:astro-ph/0611774v210Jan2007 Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

arXiv:astro-ph/0611774v210Jan2007 Gamma-Ray Burst Afterglows Bing Zhang Department of Physics in multi-wavelength are observed following Gamma-ray bursts (GRBs). Recent broad- band observational with the ambient medium. Key words: Gamma-Ray Bursts, Swift Observatory, X-rays, optical, radio 1. Introduction

Zhang, Bing

353

Studies of Gamma-Ray Burst Prompt Emission with RHESSI and NCT  

E-Print Network (OSTI)

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

Bellm, Eric Christopher

2011-01-01T23:59:59.000Z

354

Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro  

E-Print Network (OSTI)

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

California at Santa Cruz, University of

355

Did a gamma-ray burst initiate the late Ordovician mass extinction?  

E-Print Network (OSTI)

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

Jackman, Charles H.

356

Extrapolations of BATSE Gamma-Ray Burst Spectra to the Optical-UV Band  

E-Print Network (OSTI)

Many gamma-ray burst counterpart searches are being conducted in the optical-UV band. To both predict detectability and understand the meaning of any detections or upper limits, we extrapolate gamma-ray spectra from 54 bright gamma-ray bursts to optical-UV energies. We assume optical emission is concurrent with gamma-ray emission and do not consider quiescent or fading counterparts. We find that the spectrum must be steeper (greater flux at low energy) than a simple extrapolation of the gamma-ray spectrum for more than one simultaneous optical flash to be observable per year by current searches.

Lyle Ford; David Band

1996-07-10T23:59:59.000Z

357

Gamma-ray bursts, axion emission and string theory dilaton  

E-Print Network (OSTI)

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.

O. Bertolami

1999-01-14T23:59:59.000Z

358

Neutron and Gamma Ray Pulse Shape Discrimination with Polyvinyltoluene  

SciTech Connect

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.

Lintereur, Azaree T.; Ely, James H.; Stave, Jean A.; McDonald, Benjamin S.

2012-03-01T23:59:59.000Z

359

Radiation detection system for portable gamma-ray spectroscopy  

DOE Patents (OSTI)

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.

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

360

Photospheric signatures imprinted on the gamma-ray burst spectra  

E-Print Network (OSTI)

A solution is presented for the spectrum of high-energy gamma-ray burst photons confined to a quasi-thermal baryonic photosphere. The solution is valid in the steady-state limit assuming the region under consideration is optically thick to the continuously injected photons. It is shown that for a high luminosity photosphere, the non-thermal electrons resulting from gamma-ray Compton cooling lose their energy by upscattering the soft thermalised radiation. The resulting spectral modifications offer the possibility of diagnosing not only the burst comoving luminosity but also the baryon load of the ejecta. This model leads to a simple physical interpretation of X-ray rich bursts and anomalous low-energy slopes.

Enrico Ramirez-Ruiz

2005-09-08T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Stochastic wake field particle acceleration in Gamma-Ray Bursts  

E-Print Network (OSTI)

Gamma-Ray Burst (GRB) prompt emission can, for specific conditions, be so powerful and short-pulsed to strongly influence any surrounding plasma. In this paper, we briefly discuss the possibility that a very intense initial burst of radiation produced by GRBs satisfy the intensity and temporal conditions to cause stochastic wake-field particle acceleration in a surrounding plasma of moderate density. Recent laboratory experiments clearly indicate that powerful laser beam pulses of tens of femtosecond duration hitting on target plasmas cause efficient particle acceleration and betatron radiation up to tens of MeV. We consider a simple but realistic GRB model for which particle wake-field acceleration can first be excited by a very strong low-energy precursor, and then be effective in producing the observed prompt X-ray and gamma-ray GRB emission. We also briefly discuss some of the consequences of this novel GRB emission mechanism.

G. Barbiellini; F. Longo; N. Omodei; A. Celotti; M. Tavani

2006-04-11T23:59:59.000Z

362

Power Density Spectra of Gamma-Ray Bursts  

E-Print Network (OSTI)

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\

Andrei M. Beloborodov

1999-11-08T23:59:59.000Z

363

Color Superconductivity in Compact Stars and Gamma Ray Bursts  

E-Print Network (OSTI)

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.

A. Drago; A. Lavagno; G. Pagliara

2003-04-08T23:59:59.000Z

364

Fiber fed x-ray/gamma ray imaging apparatus  

SciTech Connect

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.

Hailey, Charles J. (San Francisco, CA); Ziock, Klaus-Peter (Livermore, CA)

1992-01-01T23:59:59.000Z

365

Quark Stars as inner engines for Gamma Ray Bursts?  

E-Print Network (OSTI)

A model for Gamma ray bursts inner engine based on quark stars (speculated to exist in nature) is presented. We describe how and why these objects might constitute new candidates for GRB inner engines. At the heart of the model is the onset of exotic phases of quark matter at the surface of such stars, in particular the 2-flavor color superconductivity. A novel feature of such a phase is the generation of particles which are unstable to photon decay providing a natural mechanism for a fireball generation; an approach which is fundamentally different from models where the fireball is generated during collapse or conversion of neutron star to quark star processes. The model is capable of reproducing crucial features of Gamma ray bursts, such as the episodic activity of the engine (multiple and random shell emission) and the two distinct categories of the bursts (two regimes are isolated in the model with \\sim 2 s and \\sim 81 s burst total duration).

R. Ouyed; F. Sannino

2001-03-01T23:59:59.000Z

366

Gamma-ray Emission from Crushed Clouds in Supernova Remnants  

E-Print Network (OSTI)

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 neutral pions 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.

Uchiyama, Yasunobu; Funk, Stefan; Tajima, Hiroyasu; Tanaka, Takaaki

2010-01-01T23:59:59.000Z

367

SLAC National Accelerator Laboratory - The Universe Through Fermi...  

NLE Websites -- All DOE Office Websites (Extended Search)

Five Years By Lori Ann White August 22, 2013 On June 11, 2008, what was then the Gamma-ray Large Area Space Telescope rode a Delta II rocket into low-Earth orbit. After two...

368

Dark gamma-ray bursts: possible role of multiphoton processes  

E-Print Network (OSTI)

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.

Mark E. Perel'man

2009-07-27T23:59:59.000Z

369

Radiation from Poynting Flux Acceleration and Gamma-Ray Bursts  

E-Print Network (OSTI)

We compute the radiation output of electrons accelerated by Poynting flux numerically from Particle-In-Cell simulations, and derive an analytic formula to explain these numerical results. We show that the in-situ power output and critical frequency are much below those predicted by the classical synchrotron formulae. We then apply these results to a model of long gamma-ray bursts. This model predicts spectral break energies remarkably consistent with the observed values.

Liang, Edison

2007-01-01T23:59:59.000Z

370

High energy particles from gamma-ray bursts  

E-Print Network (OSTI)

A review is presented of the fireball model of gamma-ray bursts (GRBs), and of the production in GRB fireballs of high energy protons and neutrinos. Constraints imposed on the model by recent afterglow observations, which support the association of GRB and ultra-high energy cosmic-ray (UHECR) sources, are discussed. Predictions of the GRB model for UHECR production, which can be tested with planned large area UHECR detectors and with planned high energy neutrino telescopes, are reviewed.

Eli Waxman

2001-03-13T23:59:59.000Z

371

Gamma-Ray Burst Detection with INTEGRAL/SPI  

E-Print Network (OSTI)

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.

Andreas von Kienlin; Nikolas Arend; Giselher Lichti; Andrew Strong; Paul Connell

2004-07-05T23:59:59.000Z

372

Search for neutrinos from Gamma-Ray Bursts with ANTARES  

E-Print Network (OSTI)

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.

Eleonora Presani

2011-04-20T23:59:59.000Z

373

Hints of the Existence of Axion-Like-Particles From the Gamma-Ray Spectra of Cosmological Sources  

Science Conference Proceedings (OSTI)

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.

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

374

The Gamma Ray Burst Rate at High Photon Energies  

E-Print Network (OSTI)

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.

Karl Mannheim; Dieter Hartmann; Burkhardt Funk

1996-05-17T23:59:59.000Z

375

Gamma-Ray Bursts Above 1 GeV  

E-Print Network (OSTI)

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.

Matthew G. Baring

1997-11-21T23:59:59.000Z

376

GAMMA-RAY BURSTS FROM NEUTRON STAR BINARIES  

E-Print Network (OSTI)

We report on general relativistic hydrodynamic studies which indicate several new physical processes which may contribute to powering gamma-ray bursts in neutron star binaries. Relativistically driven compression, heating, and collapse of the individual stars can occur many seconds before inspiral and merger. This compression may produce a neutrino burst of ? 10 53 ergs lasting several seconds. The associated thermal neutrino emission produces an e + ? e ? pair plasma by ?¯? annihilation. We show first results of a simulated burst which produces ? 10 51 erg in ?-rays. We also discuss a preliminary study of the evolution of the magnetic field lines attached to the fluid as the stars orbit. We show that the relativistically driven fluid motion might lead to the formation of extremely strong magnetic fields ( ? 10 17 gauss) in and around the stars which could affect to the formation and evolution of a gamma-ray burst. It has been speculated for some time that inspiraling neutron stars could provide a power source for cosmological gamma-ray bursts. The rate of neutron star mergers (when integrated over the number of galaxies out to high redshift) could account for the observed GRB event rate. The possibility that at least some ?-ray bursts involve

G. J. Mathews

1997-01-01T23:59:59.000Z

377

Are we observing Lorentz violation in gamma ray bursts?  

E-Print Network (OSTI)

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.

Theodore G. Pavlopoulos

2005-08-12T23:59:59.000Z

378

Development of Compton gamma-ray sources at LLNL  

SciTech Connect

Compact Compton scattering gamma-ray sources offer the potential of studying nuclear photonics with new tools. The optimization of such sources depends on the final application, but generally requires maximizing the spectral density (photons/eV) of the gamma-ray beam while simultaneously reducing the overall bandwidth on target to minimize noise. We have developed an advanced design for one such system, comprising the RF drive, photoinjector, accelerator, and electron-generating and electron-scattering laser systems. This system uses a 120 Hz, 250 pC, 2 ps, 0.35 mm mrad electron beam with 250 MeV maximum energy in an X-band accelerator scattering off a 150 mJ, 10 ps, 532 nm laser to generate 5 Multiplication-Sign 10{sup 10} photons/eV/s/Sr at 0.5 MeV with an overall bandwidth of less than 1%. The source will be able to produce photons up to energies of 2.5 MeV. We also discuss Compton scattering gamma-ray source predictions given by numerical codes.

Albert, F.; Anderson, S. G.; Ebbers, C. A.; Gibson, D. J.; Hartemann, F. V.; Marsh, R. A.; Messerly, M. J.; Prantil, M. A.; Wu, S.; Barty, C. P. J. [Lawrence Livermore National Laboratory, NIF and Photon Science, 7000 East avenue, Livermore, CA 94550 (United States)

2012-12-21T23:59:59.000Z

379

Extending the Fermi-LAT Data Processing Pipeline to the Grid  

E-Print Network (OSTI)

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)

Stephan Zimmer; Luisa Arrabito; Tom Glanzman; Tony Johnson; Claudia Lavalley; Andrei Tsaregorodtsev

2012-12-17T23:59:59.000Z

380

ON THE RECENTLY DISCOVERED CORRELATIONS BETWEEN GAMMA-RAY AND X-RAY PROPERTIES OF GAMMA-RAY BURSTS  

SciTech Connect

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.

Dado, Shlomo; Dar, Arnon [Physics Department, Technion, Haifa 32000 (Israel)

2013-09-20T23:59:59.000Z

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381

Ultra-high energy cosmic rays, cascade gamma-rays, and high-energy neutrinos from gamma-ray bursts  

E-Print Network (OSTI)

Gamma-ray bursts (GRBs) are sources of energetic, highly variable fluxes of gamma rays, which demonstrates that they are powerful particle accelerators. Besides relativistic electrons, GRBs should also accelerate high-energy hadrons, some of which could escape cooling to produce ultra-high energy cosmic rays (UHECRs). Acceleration of high-energy hadrons in GRB blast waves will be established if high-energy neutrinos produced through photopion interactions in the blast wave are detected from GRBs. Limitations on the energy in nonthermal hadrons and the number of expected neutrinos are imposed by the fluxes from pair-photon cascades initiated in the same processes that produce neutrinos. Only the most powerful bursts at fluence levels >~ 3e-4 erg/cm^2 offer a realistic prospect for detection of >> TeV neutrinos. Detection of high-energy neutrinos is likely if GRB blast waves have large baryon loads and Doppler factors <~ 200. Cascade gamma rays will accompany neutrino production and might already have been detected as anomalous emission components in the spectra of some GRBs. Prospects for detection of GRBs in the Milky Way are also considered.

Charles D. Dermer; Armen Atoyan

2006-06-26T23:59:59.000Z

382

GRB 050117: SIMULTANEOUS GAMMA-RAY AND X-RAY OBSERVATIONS WITH THE SWIFT SATELLITE Joanne E. Hill,1, 2  

E-Print Network (OSTI)

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

Zhang, Bing

383

Gravitational collapse of a spherical star with heat flow as a possible energy mechanism of gamma-ray bursts  

E-Print Network (OSTI)

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.

Zhe Chang; Cheng-Bo Guan; Chao-Guang Huang; Xin Li

2008-03-26T23:59:59.000Z

384

An Algorithm for Detecting Quantum-Gravity Photon Dispersion in Gamma-Ray Bursts: DISCAN  

E-Print Network (OSTI)

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.

Jeffrey D. Scargle; Jay P. Norris; Jerry T. Bonnell

2006-10-19T23:59:59.000Z

385

Fermi-LAT Observation of Quiet Solar Emission  

E-Print Network (OSTI)

The Large Area Telescope (LAT) on board Fermi has detected high-energy gamma rays from the quiet Sun produced by interactions of cosmic-ray nucleons with the solar surface and cosmic-ray electrons with solar photons in the heliosphere. Such observations provide a probe of the extreme conditions near the solar atmosphere and photosphere and permit the study of the modulation of cosmic rays over the inner heliosphere. For the first year of Fermi observations the solar modulation was at its minimum corresponding to a maximum cosmic-ray flux and, hence, maximum gamma-ray emission from the Sun. We discuss the study of the quiescent solar emission, including spectral analysis of its two components, disk and inverse Compton, using the first-year data of the mission and models using the electron spectrum measured by Fermi.

Orlando, Elena

2009-01-01T23:59:59.000Z

386

DISCOVERY OF THE OPTICAL/ULTRAVIOLET/GAMMA-RAY COUNTERPART TO THE ECLIPSING MILLISECOND PULSAR J1816+4510  

SciTech Connect

The energetic, eclipsing millisecond pulsar J1816+4510 was recently discovered in a low-frequency radio survey with the Green Bank Telescope. With an orbital period of 8.7 hr and a minimum companion mass of 0.16 M{sub Sun }, it appears to belong to an increasingly important class of pulsars that are ablating their low-mass companions. We report the discovery of the {gamma}-ray counterpart to this pulsar and present a likely optical/ultraviolet counterpart as well. Using the radio ephemeris, we detect pulsations in the unclassified {gamma}-ray source 2FGL J1816.5+4511, implying an efficiency of {approx}25% in converting the pulsar's spin-down luminosity into {gamma}-rays and adding PSR J1816+4510 to the large number of millisecond pulsars detected by Fermi. The likely optical/UV counterpart was identified through position coincidence (<0.''1) and unusual colors. Assuming that it is the companion, with R = 18.27 {+-} 0.03 mag and effective temperature {approx}> 15,000 K, it would be among the brightest and hottest of low-mass pulsar companions and appears qualitatively different from other eclipsing pulsar systems. In particular, current data suggest that it is a factor of two larger than most white dwarfs of its mass but a factor of four smaller than its Roche lobe. We discuss possible reasons for its high temperature and odd size, and suggest that it recently underwent a violent episode of mass loss. Regardless of origin, its brightness and the relative unimportance of irradiation make it an ideal target for a mass, and hence a neutron star mass, determination.

Kaplan, D. L.; Kotulla, R.; Biwer, C. M.; Day, D. F. [Physics Department, University of Wisconsin-Milwaukee, Milwaukee WI 53211 (United States); Stovall, K.; Dartez, L.; Ford, A. J.; Garcia, A.; Jenet, F. A. [Center for Advanced Radio Astronomy and Department of Physics and Astronomy, University of Texas at Brownsville, Brownsville, TX 78520 (United States); Ransom, S. M. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22901 (United States); Roberts, M. S. E. [Eureka Scientific, Inc., 2452 Delmer Street, Suite 100, Oakland, CA 94602-3017 (United States); Archibald, A. M.; Karako, C.; Kaspi, V. M.; Lynch, R. S. [Department of Physics, McGill University, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Boyles, J.; Lorimer, D. R.; McLaughlin, M. A. [Department of Physics, West Virginia University, White Hall, 115 Willey Street, Morgantown, WV 26506 (United States); Hessels, J. W. T.; Kondratiev, V. I., E-mail: kaplan@uwm.edu [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); and others

2012-07-10T23:59:59.000Z

387

Gamma-ray Bursts Produced by Mirror Stars  

E-Print Network (OSTI)

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.

S. Blinnikov

1999-02-21T23:59:59.000Z

388

Gamma-Ray Bursts and Dark Matter - a joint origin?  

E-Print Network (OSTI)

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.

Daniel Enstrom

1998-10-13T23:59:59.000Z

389

Gamma-ray bursts and the sociology of science  

E-Print Network (OSTI)

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.

A. De Rujula

2003-06-16T23:59:59.000Z

390

Gamma-rays from PSR B1259 -63  

E-Print Network (OSTI)

The high-energy gamma-ray emission discovered using the H.E.S.S. telescopes from the binary system PSR B1259 -63, is modelled using an extension of the approach that successfully predicted it. We find that the simultaneous INTEGRAL and H.E.S.S. data permit both a model with dominant radiative losses, high pulsar wind Lorentz factor and modest efficiency as well as one with dominant adiabatic losses, a slower wind and higher efficiency. Additional, simultaneous, X-ray and TeV data sets are needed to lift this degeneracy.

J. G. Kirk; Lewis Ball; S. Johnston

2005-09-30T23:59:59.000Z

391

Can Sequentially Linked Gamma-Ray Bursts Nullify Randomness?  

E-Print Network (OSTI)

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.

Charles Fleischer

2012-05-02T23:59:59.000Z

392

High Energy Neutrinos from Cosmological Gamma-Ray Burst Fireballs  

E-Print Network (OSTI)

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.

Eli Waxman; John Bahcall

1997-01-30T23:59:59.000Z

393

Ultra high energy neutrinos from gamma ray bursts  

E-Print Network (OSTI)

Protons accelerated to high energies in the relativistic shocks that generate gamma ray bursts photoproduce pions, and then neutrinos in situ. I show that ultra high energy neutrinos (> 10^19 eV) are produced during the burst and the afterglow. A larger flux, also from bursts, is generated via photoproduction off CMBR photons in flight but is not correlated with currently observable bursts, appearing as a bright background. Adiabatic/synchrotron losses from protons/pions/muons are negligible. Temporal and directional coincidences with bursts detected by satellites can separate correlated neutrinos from the background.

Mario Vietri

1998-02-18T23:59:59.000Z

394

Gamma-Ray Bursts and Quantum Cosmic Censorship  

E-Print Network (OSTI)

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.

T. P. Singh

1998-05-17T23:59:59.000Z

395

Gravitational radiation from long gamma-ray bursts  

E-Print Network (OSTI)

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.

Maurice H. P. M. van Putten

2001-02-11T23:59:59.000Z

396

Virtual Gamma Ray Radiation Sources through Neutron Radiative Capture  

SciTech Connect

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.

Scott Wilde, Raymond Keegan

2008-07-01T23:59:59.000Z

397

INTERPLANETARY NETWORK LOCALIZATIONS OF KONUS SHORT GAMMA-RAY BURSTS  

SciTech Connect

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.

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

398

Gamma-Ray Bursts and Dark Energy - Dark Matter interaction  

E-Print Network (OSTI)

In this work Gamma Ray Burst (GRB) data is used to place constraints on a putative coupling between dark energy and dark matter. Type Ia supernovae (SNe Ia) constraints from the Sloan Digital Sky Survey II (SDSS-II) first-year results, the cosmic microwave background radiation (CMBR) shift parameter from WMAP seven year results and the baryon acoustic oscillation (BAO) peak from the Sloan Digital Sky Survey (SDSS) are also discussed. The prospects for the field are assessed, as more GRB events become available.

T. Barreiro; O. Bertolami; P. Torres

2010-04-26T23:59:59.000Z

399

Are Durations of Weak Gamma-Ray Bursts Reliable?  

E-Print Network (OSTI)

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.

Maarten Schmidt

2005-08-16T23:59:59.000Z

400

Gamma ray burst distances and the timescape cosmology  

E-Print Network (OSTI)

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.

Peter R. Smale

2011-07-27T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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401

KINEMATIC ORIGIN OF CORRELATIONS BETWEEN GAMMA-RAY BURST OBSERVABLES  

Science Conference Proceedings (OSTI)

Recently, several new correlations between gamma-ray burst (GRB) observables have been discovered. Like previously well-established correlations, they challenge GRB models. Here, we show that in the cannonball (CB) model of GRBs, the newly discovered correlations have the same simple kinematic origin as those discovered earlier. They all result from the strong dependence of the observed radiations on the Lorentz and Doppler factors of the jet of highly relativistic plasmoids (CBs) that produces the observed radiations by interaction with the medium through which it propagates.

Dado, Shlomo; Dar, Arnon, E-mail: dado@phep3.technion.ac.il, E-mail: arnon@physics.technion.ac.il [Physics Department, Technion, Haifa 32000 (Israel)

2012-04-20T23:59:59.000Z

402

Contemporaneous observations of the radio galaxy NGC 1275 from radio to very high energy gamma-rays  

E-Print Network (OSTI)

The radio galaxy NGC 1275, recently identified as a very high energy (VHE, >100 GeV) gamma-ray emitter by MAGIC, is one of the few non-blazar AGN detected in the VHE regime. In order to better understand the origin of the gamma-ray emission and locate it within the galaxy, we study contemporaneous multi-frequency observations of NGC 1275 and model the overall spectral energy distribution (SED). We analyze unpublished MAGIC observations carried out between Oct. 2009 and Feb. 2010, and the already published ones taken between Aug. 2010 and Feb. 2011. We study the multi-band variability and correlations analyzing data of Fermi-LAT (0.1 - 100 GeV), Chandra (X-ray), KVA (optical) and MOJAVE (radio) taken during the same period. Using custom Monte Carlo simulations corresponding to early MAGIC stereo data, we detect NGC 1275 also in the earlier MAGIC campaign. The flux level and energy spectra are similar to the results of the second campaign. The monthly light curve above 100 GeV shows a hint of variability at the...

Aleksi?, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giavitto, G; Godinovi?, N; Muñoz, A González; Gozzini, S R; Hadamek, A; Hadasch, D; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Knoetig, M L; Krause, J; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, K; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Sun, S; Suri?, T; Takalo, L; Tavecchio, F; Temnikov, P; Terzi?, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Balmaverde, B; Kataoka, J; Rekola, R; Takahashi, Y; .,

2013-01-01T23:59:59.000Z

403

A Comprehensive Search for Gamma-Ray Lines in the First Year of Data from the INTEGRAL Spectrometer  

E-Print Network (OSTI)

We have carried out an extensive search for gamma-ray lines in the first year of public data from the Spectrometer (SPI) on the INTEGRAL mission. INTEGRAL has spent a large fraction of its observing time in the Galactic Plane with particular concentration in the Galactic Center (GC) region (~ 3 Msec in the first year). Hence the most sensitive search regions are in the Galactic Plane and Center. The phase space of the search spans the energy range 20-8000 keV and line widths from 0-1000 keV (FWHM). It includes both diffuse and point-like emission. We have searched for variable emission on time scales down to ~ 1000 sec. Diffuse emission has been searched for on a range of different spatial scales from ~ 20 deg (the approximate field-of-view of the spectrometer) up to the entire Galactic Plane. Our search procedures were verified by the recovery of the known gamma-ray lines at 511 keV and 1809 keV at the appropriate intensities and significances. We find no evidence for any previously unknown gamma-ray lines. The upper limits range from a few x 10^-5 cm^-2 s^-1 to a few x 10^-2 cm^-2 s^-1 depending on line width, energy and exposure; regions of strong instrumental background lines were excluded from the search. Comparison is made between our results and various prior predictions of astrophysical lines.

B. J. Teegarden; K. Watanabe

2006-04-12T23:59:59.000Z

404

Brief Studying of Oil Crust Thickness Measurement by Gamma Ray Compton Scattering Approach  

E-Print Network (OSTI)

The relation between the scattering cross section and the scattering angle under different energy condition of the incident rays is analyzed. From Compton scattering total cross section, a formula of quasi-parallel incident gamma ray Compton scattering response function versus to thickness of oil crust target is derived and analyzed. Numerical fitting result shows that there exists cubic relation between response function of gamma ray and thickness of oil crust. Key words: Gamma ray, Compton scattering, oil crust

Mamatrishat, Mamat; Jie, Ding; Shiheng, Wang

2008-01-01T23:59:59.000Z

405

Milagro Search for Very High Energy Emission from Gamma-Ray Bursts in the Swift Era  

E-Print Network (OSTI)

2005. 1. Me´sza´ros, P. & Rees, M. Optical and long-wavelength afterglow from gamma- ray bursts model. Astrophys. J. 517, L109­-L112 (1999). 3. Ford, L. A. et al. BATSE observations of gamma-ray burst, F. et al. Spectral properties of the prompt X-ray emission and afterglow from the gamma-ray burst

California at Santa Cruz, University of

406

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF GRB 110625A  

SciTech Connect

Gamma-ray bursts (GRBs) that emit photons at GeV energies form a small but significant population of GRBs. However, the number of GRBs whose GeV-emitting period is simultaneously observed in X-rays remains small. We report {gamma}-ray observations of GRB 110625A using Fermi's Large Area Telescope in the energy range 100 MeV-20 GeV. Gamma-ray emission at these energies was clearly detected using data taken between 180 s and 580 s after the burst, an epoch after the prompt emission phase. The GeV light curve differs from a simple power-law decay, and probably consists of two emission periods. Simultaneous Swift X-Ray Telescope observations did not show flaring behaviors as in the case of GRB 100728A. We discuss the possibility that the GeV emission is the synchrotron self-Compton radiation of underlying ultraviolet flares.

Tam, P. H. T.; Kong, A. K. H. [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Fan Yizhong, E-mail: phtam@phys.nthu.edu.tw [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2012-08-01T23:59:59.000Z

407

The On-Orbit Calibrations for the Fermi Large Area Telescope  

SciTech Connect

The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope began its on-orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here we describe on-orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be described in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. These results have been used to calibrate the LAT datasets to be publicly released in August 2009.

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.; Ampe, J.; /Naval Research Lab, Wash., D.C.; Anderson, B.; /UC, Santa Cruz; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U., OKC /Stockholm U.; Bagagli, R.; /INFN, Pisa; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bartelt, J.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bederede, D.; /DAPNIA, Saclay; Bellardi, F.; /INFN, Pisa; Bellazzini, R.; /INFN, Pisa; Belli, F.; /Frascati /Rome U.,Tor Vergata; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bisello, D.; /INFN, Padua /Padua U. /Garching, Max Planck Inst., MPE /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /DAPNIA, Saclay /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Pisa /INFN, Pisa /Bari U. /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /INFN, Padua /Padua U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /Kalmar U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /DAPNIA, Saclay /ASDC, Frascati /INFN, Pisa /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. /DAPNIA, Saclay /NASA, Goddard /INFN, Perugia /Perugia U.; /more authors..

2011-11-17T23:59:59.000Z

408

Constraining Pulsar Emission Physics through Radio/Gamma-Ray Correlation of Crab Giant Pulses  

E-Print Network (OSTI)

To constrain the giant pulse (GP) emission mechanism and test the model of Lyutikov (2007) of GP emission, we are carrying out a campaign of simultaneous observations of the Crab pulsar between gamma-rays (Fermi) and radio wavelengths. The correlation between times of arrival of radio GPs and high-energy photons, whether it exists or not, will allow us to choose between different origins of GP emission and further constrain the emission physics. Our foremost goal was testing whether radio GPs are due to changes in the coherence of the radio emission mechanism, variations in the pair creation rate in the pulsar magnetosphere, or changes in the beaming direction. Accomplishing this goal requires an enormous number of simultaneous radio GPs and gamma-photons. Thus, we organized a radio observations campaign using the 42-ft telescope at the Jodrell Bank Observatory (UK), the 140-ft telescope, and the 100-m Richard C. Byrd Green Bank Telescope (GBT) at the Green Bank Observatory (WV). While the observations with t...

Bilous, A V; McLaughlin, M A; Mickaliger, M; Lorimer, D R; Ransom, S M; Lyutikov, M; Stappers, B; Langston, G I

2009-01-01T23:59:59.000Z

409

Pair-production opacity at high and very-high gamma-ray energies  

E-Print Network (OSTI)

The propagation of high energy (HE, $E_\\gamma>100$ MeV) and very high-energy gamma-rays (VHE, $E_\\gamma>100$ GeV) in the extra-galactic photon field leads to pair-production and consequently energy- and distance-dependent attenuation of the primary intensity. The spectroscopy of an increasing number of extra-galactic objects at HE and VHE energies has demonstrated indeed the presence of such an attenuation which in turn has been used to constrain the photon density in the medium. At large optical depth ($\\tau\\gtrsim 2$) potential modifications of pair-production due to competing but rare processes (as, e.g., the presence of sub-neV axion-like particle) may be found. Indications for a pair-production anomaly have previously been found with VHE-spectra. Here, we present further indications (at the level of $3.68 \\sigma$) for a reduced optical depth at high energies from an analysis of Fermi-\\textit{LAT} data.

Dieter Horns; Manuel Meyer

2013-09-16T23:59:59.000Z

410

ON THE ORIGIN OF > 10 GeV PHOTONS IN GAMMA-RAY BURST AFTERGLOWS  

Science Conference Proceedings (OSTI)

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.

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

411

Probing Charged Matter Through Higgs Diphoton Decay, Gamma Ray Lines, and EDMs  

E-Print Network (OSTI)

Numerous experiments currently underway offer the potential to indirectly probe new charged particles with masses at the weak scale. For example, the tentative excess in Higgs diphoton decay and the tentative gamma-ray line in Fermi-LAT data have recently attracted attention as possible one-loop signatures of new charged particles. We explore the interplay between such signals, dark matter direct detection through Higgs exchange, and measurements of the electron EDM, by studying the size of these effects in several models. We compute one-loop effects to explore the relationship among couplings probed by different experiments. In particular, models in which dark matter and the Higgs both interact with charged particles at a detectable level typically induce, at loop level, couplings between dark matter and the Higgs that are around the level of current direct detection sensitivity. Intriguingly, one-loop Higgs diphoton decay and DM annihilation into two photons, two-loop EDMs, and loop-induced direct detection rates are all coming within range of existing experiments for approximately the same range of charged particle masses, offering the prospect of an exciting coincidence of signals at collider, astrophysical, underground and atomic physics measurements.

JiJi Fan; Matthew Reece

2013-01-11T23:59:59.000Z

412

Studies of Gamma-Ray Burst Prompt Emission with RHESSI and NCT.  

E-Print Network (OSTI)

??Gamma-Ray Bursts (GRBs) are the most luminous objects in the universe. They herald a catastrophic energy release which manifests itself in tenths to hundreds of… (more)

Bellm, Eric Christopher

2011-01-01T23:59:59.000Z

413

Gamma-Ray Burst Afterglows as probes of their host galaxies and the Cosmos.  

E-Print Network (OSTI)

??Gamma-ray Bursts (GRBs) represent the sole class of catastrophic phenomena seen over almost the entire history of the Universe. Their extreme luminosities in high energy… (more)

Cucchiara, Antonino

2010-01-01T23:59:59.000Z

414

Gamma-ray bursts and their afterglows: toward a unified model.  

E-Print Network (OSTI)

??Although much progress has been made in our understanding of gamma-ray bursts (GRBs) and their afterglows in the last few decades, some critical questions remain… (more)

McMahon, Erin Malia, 1980-

2008-01-01T23:59:59.000Z

415

Swift Pointing and the Association Between Gamma-Ray Bursts and Gravitational-Wave Bursts  

E-Print Network (OSTI)

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.

Lee Samuel Finn; Badri Krishnan; Patrick J. Sutton

2003-04-11T23:59:59.000Z

416

Are Short and Long Gamma Ray Bursts Really of Different Origin?  

E-Print Network (OSTI)

It is shown that short and long gamma ray bursts (GRBs) are of the same origin and, furthermore, correlated with their duration.

Ernst Karl Kunst

2000-12-06T23:59:59.000Z

417

An Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemic...  

Open Energy Info (EERE)

are fairly rich in radioelement concentrations. The aerial gamma-ray spectrometric survey data, gathered for the purpose of radioactive mineral exploration were utilized as an...

418

Testing and Improving the Luminosity Relations for Gamma-Ray Bursts.  

E-Print Network (OSTI)

??Gamma Ray Bursts (GRBs) have several luminosity relations where a measurable property of a burst light curve or spectrum is correlated with the burst luminosity.… (more)

Collazzi, Andrew

2011-01-01T23:59:59.000Z

419

The investigation of intrinsic spectral and temporal properties of gamma-ray bursts .  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs) have become a truly unique puzzle in Astronomy. Unlike quasars and pulsars which were explained within years of their discovery, the origins… (more)

[No author

2005-01-01T23:59:59.000Z

420

Fission prompt gamma-ray multiplicity distribution measurements and simulations at DANCE  

SciTech Connect

The nearly energy independence of the DANCE efficiency and multiplicity response to {gamma} rays makes it possible to measure the prompt {gamma}-ray multiplicity distribution in fission. We demonstrate this unique capability of DANCE through the comparison of {gamma}-ray energy and multiplicity distribution between the measurement and numerical simulation for three radioactive sources {sup 22}Na, {sup 60}Co, and {sup 88}Y. The prospect for measuring the {gamma}-ray multiplicity distribution for both spontaneous and neutron-induced fission is discussed.

Chyzh, A; Wu, C Y; Ullmann, J; Jandel, M; Bredeweg, T; Couture, A; Norman, E

2010-08-24T23:59:59.000Z

Note: This page contains sample records for the topic "fermi gamma-ray space" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

The Sample of Gamma-ray Bursts Observed With SPI-ACS  

E-Print Network (OSTI)

The SPI anticoincidence shield consists of 91 BGO crystals and is operated as a nearly omnidirectional gamma-ray burst detector above ~75 keV. Since the start of the mission 269 gamma-ray burst candidates have been detected. 110 bursts have been confirmed with the instruments included in the 3rd Interplanetary Network. Here we present a preliminary statistical analysis of the SPI-ACS sample of gamma-ray bursts and gamma-ray burst candidates; in particular we discuss the duration distribution of the bursts. A prominent population of short burst candidates (duration ray nuclei interacting in the detectors.

A. Rau; A. von Kienlin; K. Hurley; G. G. Lichti

2004-05-06T23:59:59.000Z

422

Once again on the duration of nuclear gamma-ray-emission and gamma-ray-absorption processes  

SciTech Connect

In addition to previous indications of a long-term character of the processes of gamma-ray emission and absorption by nuclei, another two simple arguments in support of this picture are presented. It is shown that the Fourier integral for a short wave train is a frequency distribution whose width is many orders of magnitude larger than actual intrinsic widths of gamma lines. The uncertainty in the photon spatial position is found to be about {tau}c, which is the length of the wave train emitted by a nucleus over the average lifetime {tau} of this nucleus in an excited state.

Davydov, A. V., E-mail: andrey.davydov@itep.ru [Institute of Theoretical and Experimental Physics (Russian Federation)

2011-01-15T23:59:59.000Z

423

Binary Pulsar Shock Emissions as Galactic Gamma-Ray Sources  

E-Print Network (OSTI)

We address several issues regarding the interpretation of galactic \\ggg-ray sources. We consider powerful pulsars in binaries producing X-ray and gamma-ray {\\it unpulsed} emission from the shock interaction of relativistic pulsar winds with circumbinary material. Nebular mass outflows from companion stars of binary pulsars can provide the right {\\it calorimeters} to transform a fraction of the electromagnetic and kinetic energy of pulsar winds into high energy radiation. We discuss the physics of interaction of relativistic pulsar winds with gaseous material and show that the conditions in pulsar binary systems might be ideal to constrain shock acceleration mechanisms and pulsar wind composition and structure. We briefly discuss the example of the 47~ms pulsar PSR~1259-63 orbiting around a massive Be~star companion and monitored by X-ray and gamma-ray instruments during its recent periastron passage. In addition to young pulsars in massive binaries, also a class of recycled millisecond pulsars in low-mass binaries can be interesting high energy emitters.

M. Tavani

1995-02-10T23:59:59.000Z

424

Binary pulsar shock emissions as galactic gamma-ray sources  

E-Print Network (OSTI)

We address several issues regarding the interpretation of galactic \\ggg-ray sources. We consider powerful pulsars in binaries producing X-ray and gamma-ray {\\it unpulsed} emission from the shock interaction of relativistic pulsar winds with circumbinary material. Nebular mass outflows from companion stars of binary pulsars can provide the right {\\it calorimeters} to transform a fraction of the electromagnetic and kinetic energy of pulsar winds into high energy radiation. We discuss the physics of interaction of relativistic pulsar winds with gaseous material and show that the conditions in pulsar binary systems might be ideal to constrain shock acceleration mechanisms and pulsar wind composition and structure. We briefly discuss the example of the 47~ms pulsar PSR~1259-63 orbiting around a massive Be~star companion and monitored by X-ray and gamma-ray instruments during its recent periastron passage. In addition to young pulsars in massive binaries, also a class of recycled millisecond pulsars in low-mass bin...

Tavani, M

1995-01-01T23:59:59.000Z

425

A Cautionary Note on Gamma Ray Burst Nearest Neighbor Statistics  

E-Print Network (OSTI)

In this letter we explore the suggestion of Quashnock and Lamb (1993) that nearest neighbor correlations among gamma ray burst positions indicate the possibility of burst repetitions within various burst sub-classes. With the aid of Monte Carlo calculations we compare the observed nearest neighbor distributions with those expected from an isotropic source population weighted by the published BATSE exposure map. The significance of the results are assessed via the Kolmogorov-Smirnov (K-S) test, as well as by a comparison to Monte Carlo simulations. The K-S results are in basic agreement with those of Quashnock and Lamb. However, as Narayan and Piran (1993) point out, and the Monte Carlo calculations confirm, the K-S test overestimates the significance of the observed distributions. We compare the sensitivity of these results to both the definitions of the assumed burst sub-classes and the burst positional errors. Of the two, the positional errors are more significant and indicate that the results of Quashnock and Lamb may be due to systematic errors, rather than any intrinsic correlation among the burst positions. Monte Carlo simulations also show that with the current systematic errors, the nearest neighbor statistic is not very sensitive to moderate repetition rates. Until the BATSE statistical and systematic errors are fully understood, the burst nearest neighbor correlations cannot be claimed to be significant evidence for burst repetitions. Subject Headings: gamma rays: bursts — methods: statistical

Michael A. Nowak

1993-01-01T23:59:59.000Z

426

Are There MeV Gamma-Ray Bursts?  

E-Print Network (OSTI)

It is often stated that gamma-ray bursts (GRBs) have typical energies of several hundred keV. Is this a real feature of GRBs or is it due to an observational bias? We consider the possibility that bursts of a given bolometric luminosity occur with a hardness distribution $p(H)d \\log H \\propto H^\\gamma d \\log H$. We model the detection efficiency of BATSE as a function of $H$ and calculate the expected distribution of $H$ in the observed sample for various values of $\\gamma$. We show that because the detection efficiency of BATSE falls steeply with increasing $H$, the paucity of hard bursts need not be real. We find that the observed sample is consistent with a distribution above $H = 100$ keV with $\\gamma \\approx 0$ or even $\\gamma =0.5$. Thus, a large population of unobserved hard gamma-ray bursts may exist. It is important to extend the present analysis to a larger sample of BATSE bursts and to include the OSSE and COMPTEL limits. If the full sample is consistent with $\\gamma\\ \\sgreat\\ 0$, then it would be interesting to look for MeV bursts in the future.

Tsvi Piran; Ramesh Narayan

1995-12-19T23:59:59.000Z

427

Laser System for Livermore's Mono Energetic Gamma-Ray Source  

SciTech Connect

A Mono-energetic Gamma-ray (MEGa-ray) source, based on Compton scattering of a high-intensity laser beam off a highly relativistic electron beam, requires highly specialized laser systems. To minimize the bandwidth of the {gamma}-ray beam, the scattering laser must have minimal bandwidth, but also match the electron beam depth of focus in length. This requires a {approx}1 J, 10 ps, fourier-transform-limited laser system. Also required is a high-brightness electron beam, best provided by a photoinjector. This electron source requires a second laser system with stringent requirements on the beam including flat transverse and longitudinal profiles and fast rise times. Furthermore, these systems must be synchronized to each other with ps-scale accuracy. Using a novel hyper-dispersion compressor configuration and advanced fiber amplifiers and diode-pumped Nd:YAG amplifiers, we have designed laser systems that meet these challenges for the X-band photoinjector and Compton-scattering source being built at Lawrence Livermore National Laboratory.

Gibson, D; Albert, F; Bayramian, A; Marsh, R; Messerly, M; Ebbers, C; Hartemann, F

2011-03-14T23:59:59.000Z

428

On the Bimodal Distribution of Gamma-Ray Bursts  

E-Print Network (OSTI)

Kouveliotou et al. (1993) recently confirmed that gamma-ray bursts are bimodal in duration. In this paper we compute the statistical properties of the short ($\\le 2$~s) and long ($>2$~s) bursts using a method of analysis that makes no assumption regarding the location of the bursts, whether in the Galaxy or at a cosmological distance. We find the 64 ms channel on BATSE to be more sensitive to short bursts and the 1024 ms channel is more sensitive to long bursts. We show that all the currently available data are consistent with the simple hypothesis that both short and long bursts have the same spatial distribution and that within each population the sources are standard candles. The rate of short bursts is $\\sim 0.4$ of the rate of long bursts. Although the durations of short and long gamma-ray bursts span several orders of magnitude and the total energy of a typical short burst is smaller than that of a typical long burst by a factor of $\\sim 20$, surprisingly the peak luminosities of the two kinds of bursts are equal to within a factor of $\\sim 2$.

Shude Mao; Ramesh Narayan; Tsvi Piran

1993-04-16T23:59:59.000Z

429

Gamma Ray Array Detector Trigger Sub-System  

E-Print Network (OSTI)

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.

Du Zhong-Wei; Su Hong; Qian Yi; Kong Jie

2012-11-06T23:59:59.000Z

430

Swift 1644+57: The Longest Gamma-ray Burst?  

E-Print Network (OSTI)

Swift recently discovered an unusual gamma-ray and x-ray transient (Sw 1644+57) that was initially identified as a long-duration gamma-ray burst (GRB). However, the ~ 10 keV x-ray emission has persisted for over a month with a luminosity comparable to its peak value. The astrometric coincidence of the source with the center of its host galaxy, together with other considerations, motivated the interpretation that Sw 1644+57 was produced by an outburst from a 10^{6-7} M_sun black hole at the center of the galaxy. Here we consider the alternate possibility that Sw 1644+57 is indeed a long-duration GRB, albeit a particularly long one. We discuss the general properties of very long-duration, low-power GRB-like transients associated with the core-collapse of a massive star. Both neutron star (magnetar) spindown and black hole accretion can power such events. The requirements for producing low-power, very long-duration GRBs by magnetar spindown are similar to those for powering extremely luminous supernovae by magne...

Quataert, Eliot

2011-01-01T23:59:59.000Z

431

Neutrino Emission from Gamma-Ray Burst Fireballs, Revised  

E-Print Network (OSTI)

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.

Svenja Hümmer; Philipp Baerwald; Walter Winter

2011-12-05T23:59:59.000Z

432

Design of a 2 MeV Compton scattering gamma-ray source for DNDO missions  

Science Conference Proceedings (OSTI)

Nuclear resonance fluorescence-based isotope-specific detection and imaging is a powerful new technology that can enable access to new mission spaces for DNDO. Within this context, the development of advanced mono-energetic gamma ray sources plays an important role in the DNDO R&D portfolio, as it offers a faster, more precise, and safer alternative to conventional Bremsstrahlung sources. In this report, a specific design strategy is presented, along with a series of theoretical and computational tools, with the goal of optimizing source parameters for DNDO applications. In parallel, key technologies are outlined, along with discussions justifying specific choices and contrasting those with other alternatives. Finally, a complete conceptual design is described, and machine parameters are presented in detail.

Hartemann, F V; Albert, F

2009-08-24T23:59:59.000Z

433

Nucleosynthesis of Nickel-56 from Gamma-Ray Burst Accretion Disks  

E-Print Network (OSTI)

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.

R. Surman; G. C. McLaughlin; N. Sabbatino

2011-12-12T23:59:59.000Z

434

NUCLEOSYNTHESIS OF NICKEL-56 FROM GAMMA-RAY BURST ACCRETION DISKS  

Science Conference Proceedings (OSTI)

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 M-dot = 0.05 M{sub Sun} s{sup -1} to M-dot = 1 M{sub Sun} s{sup -1}, 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.

Surman, R.; Sabbatino, N. [Department of Physics and Astronomy, Union College, Schenectady, NY 12308 (United States); McLaughlin, G. C. [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States)

2011-12-20T23:59:59.000Z

435

DELAYED ONSET OF HIGH-ENERGY EMISSIONS IN LEPTONIC AND HADRONIC MODELS OF GAMMA-RAY BURSTS  

SciTech Connect

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.

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

436

Discovery of very high energy gamma-ray emission from the blazar 1ES 1727+502 with the MAGIC Telescopes  

E-Print Network (OSTI)

Motivated by the Costamante & Ghisellini (2002) predictions we investigated if the blazar 1ES 1727+502 (z=0.055) is emitting very high energy (VHE, E>100 GeV) gamma rays. We observed the BL Lac object 1ES 1727+502 in stereoscopic mode with the two MAGIC telescopes during 14 nights between May 6th and June 10th 2011, for a total effective observing time of 12.6 hours. For the study of the multiwavelength spectral energy distribution (SED) we use simultaneous optical R-band data from the KVA telescope, archival UV/optical and X-ray observations by instruments UVOT and XRT on board of the Swift satellite and high energy (HE, 0.1 GeV - 100 GeV) gamma-ray data from the Fermi-LAT instrument. We detect, for the first time, VHE gamma-ray emission from 1ES 1727+502 at a statistical significance of 5.5 sigma. The integral flux above 150 GeV is estimated to be (2.1\\pm0.4)% of the Crab Nebula flux and the de-absorbed VHE spectrum has a photon index of (2.7\\pm0.5). No significant short-term variability was found in an...

Aleksi?, J; Antoranz, P; Asensio, M; Backes, M; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Boller, A; Bonnefoy, S; Bonnoli, G; Tridon, D Borla; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Cossio, L; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giavitto, G; Godinovi?, N; Muñoz, A González; Gozzini, S R; Hadamek, A; Hadasch, D; Häfner, D; Herrero, A; Hose, J; Hrupec, D; Idec, W; Jankowski, F; Kadenius, V; Klepser, S; Knoetig, M L; Krähenbühl, T; Krause, J; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Masbou, J; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Moldón, J; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nowak, N; Orito, R; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Puljak, I; Reichardt, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Rügamer, S; Saggion, A; Saito, K; Saito, T Y; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Spiro, S; Stamatescu, V; Stamerra, A; Steinke, B; Storz, J; Sun, S; Suri?, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzi?, T; Tescaro, D; Teshima, M; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Weitzel, Q; Zandanel, F; Zanin, R

2013-01-01T23:59:59.000Z

437

Andromeda: A mission to determine the gamma-ray burst distance scale F.A. Harrison, W.R. Cook, T.A. Prince, S.M. Schindler  

E-Print Network (OSTI)

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 high data will yield im- proved results. #12;3 5. Gamma-Ray Burst Search Sensitivity TeV gamma rays

Prince, Thomas A.

438

Gamma Ray Burst Section of the White Paper on the Status and Future of Ground-based TeV Gamma-ray Astronomy  

E-Print Network (OSTI)

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.

A. D. Falcone; D. A. Williams; M. G. Baring; R. Blandford; J. Buckley; V. Connaughton; P. Coppi; C. Dermer; B. Dingus; C. Fryer; N. Gehrels; J. Granot; D. Horan; J. I. Katz; K. Kuehn; P. Meszaros; J. Norris; P. Saz Parkinson; A. Pe'er; E. Ramirez-Ruiz; S. Razzaque; X. Y. Wang; B. Zhang

2008-10-02T23:59:59.000Z

439

Gamma Ray Burst Section of the White Paper on the Status and Future of Ground-based TeV Gamma-ray Astronomy  

E-Print Network (OSTI)

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