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Note: This page contains sample records for the topic "gamma-ray calibration blocks" from the National Library of EnergyBeta (NLEBeta).
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1

Gamma-ray energies for calibration of Ge(Li) spectrometers  

SciTech Connect

Gamma-ray energies are compared for bent-crystal measurements, Ge(Li) measurements, and other measurements. 150 gamma-ray energies below 3450 keV from 35 isotopes are being calibrated for calibration of Ge(Li) spectrometers. (WHK)

Helmer, R.G.; Greenwood, R.C.; Gehrke, R.J.

1975-01-01T23:59:59.000Z

2

Grade Assignments for Models Used for Calibration of Gross-Count Gamma-Ray Logging Systems (December 1983)  

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

Grade Assignments for Models Used for Calibration of Gross-Count Gamma-Ray Logging Systems (December 1983)

3

Uranium Enrichment Measurements without Calibration Using Gamma Rays Above 100 keV  

DOE Green Energy (OSTI)

The verification of UF{sub 6} shipping cylinders is an important activity in routine safeguards inspections. Current measurement methods using either sodium-iodide or high-purity germanium detectors require calibrations that are not always appropriate for field measurements, because of changes in geometry or container wall thickness. The introduction of the MGAU code demonstrated the usefulness of intrinsically calibrated measurements for inspections. MGAU uses the 100-keV region of the uranium gamma-ray spectrum. The thick walls of UF{sub 6} shipping cylinders and the low-energy analysis preclude the routine use of MGAU for these measurements. We have developed a uranium enrichment measurement method for measurements using high-purity germanium detectors, which do not require calibration, and uranium gamma rays above 100 keV. The method uses seven gamma rays from {sup 235}U and {sup 238}U to determine their relative detection efficiency intrinsically and with an additional gamma ray from {sup 234}U, the relative abundance of these three uranium isotopes. The method uses a function that describes the basic physical processes that predominantly determine the relative detection efficiency curve. These are the detector efficiency, the absorption by the cylinder wall, and the self-absorption by the uranium contents. We will describe this model and initial testing on various uranium materials and detector types.

Ruhter, W D; Wang, T F; Hayden, C

2001-09-27T23:59:59.000Z

4

A Brief Review of the Basis for, and the Procedures Currently Utilized in, Gross Gamma-Ray Log Calibration (October 1976)  

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

A Brief Review of the Basis for, and the Procedures Currently Utilized in, Gross Gamma-Ray Log Calibration (October 1976)

5

Reconstructing the Cosmic Expansion History up to Redshift z=6.29 with the Calibrated Gamma-Ray Bursts  

E-Print Network (OSTI)

Recently, Gamma-Ray Bursts (GRBs) were proposed to be a complementary cosmological probe to type Ia supernovae (SNIa). GRBs have been advocated to be standard candles since several empirical GRB luminosity relations were proposed as distance indicators. However, there is a so-called circularity problem in the direct use of GRBs. Recently, a new idea to calibrate GRBs in a completely cosmology independent manner has been proposed, and the circularity problem can be solved. In the present work, following the method proposed by Liang {\\it et al.}, we calibrate 70 GRBs with the Amati relation using 307 SNIa. Then, following the method proposed by Shafieloo {\\it et al.}, we smoothly reconstruct the cosmic expansion history up to redshift $z=6.29$ with the calibrated GRBs. We find some new features in the reconstructed results.

Hao Wei; Shuang Nan Zhang

2008-08-18T23:59:59.000Z

6

Locating TeV Gamma-Ray Sources with Sub-Arcminute Precision: the Pointing Calibration of the HEGRA System of Imaging Atmospheric Cherenkov Telescopes  

E-Print Network (OSTI)

Stereoscopic viewing of TeV gamma-ray air showers with systems of Imaging Atmospheric Cherenkov Telescopes (IACTs) allows to reconstruct the origin of individual primary particles with an accuracy of 0.1 degree or better. The shower impact point can be determined within 15 meters. To actually achieve this resolution, the pointing of the telescopes of an IACT system needs to be controlled with high precision. For the HEGRA IACT system, a procedure to calibrate telescope pointing was established, using bright stars distributed over the sky as references. On the basis of these measurements, one determines parameters of a correction function which is valid for the complete hemisphere. After correction a pointing accuracy of 0.01 degree is achieved.

G. Puehlhofer; A. Daum; G. Hermann; M. Hess; W. Hofmann; C. Koehler; M. Panter

1998-01-12T23:59:59.000Z

7

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

8

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

9

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

10

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

11

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

12

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

13

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

14

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

15

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

16

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

17

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

18

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

19

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

20

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


21

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

22

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

23

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

24

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

25

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

26

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

27

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

28

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

29

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

30

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

31

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

32

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

33

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

34

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

35

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

36

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

37

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

38

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

39

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

40

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


41

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

42

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

43

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

44

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...

45

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

46

The NIST Gage Block Calibration Software System User's ...  

Science Conference Proceedings (OSTI)

... The gage blocks have flat and parallel opposing ... technical staff refers as optical flats and platens. ... to the Hewlett- Packard Rocky Mountain BASIC ...

2004-07-30T23:59:59.000Z

47

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

48

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

49

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

50

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

51

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

52

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

53

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

54

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

55

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

56

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

57

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

58

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

59

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

60

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


61

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

62

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

63

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

64

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

65

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

66

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

67

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

68

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

69

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

70

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

71

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

72

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

73

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

74

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

75

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

76

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

77

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

78

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

79

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

80

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

The Use of Gamma-Ray Imaging to Improve Portal Monitor Performance  

SciTech Connect

We have constructed a prototype, rapid-deployment portal monitor that uses visible-light and gamma-ray imaging to allow simultaneous monitoring of multiple lanes of traffic from the side of a roadway. Our Roadside Tracker uses automated target acquisition and tracking (TAT) software to identify and track vehicles in visible light images. The field of view of the visible camera overlaps with and is calibrated to that of a one-dimensional gamma-ray imager. The TAT code passes information on when vehicles enter and exit the system field of view and when they cross gamma-ray pixel boundaries. Based on this in-formation, the gamma-ray imager "harvests" the gamma-ray data specific to each vehicle, integrating its radiation signature for the entire time that it is in the field of view. In this fashion we are able to generate vehicle-specific radiation signatures and avoid source confusion problems that plague nonimaging approaches to the same problem.

Ziock, Klaus-Peter [ORNL; Collins, Jeff [Lawrence Livermore National Laboratory (LLNL); Fabris, Lorenzo [ORNL; Gee, Timothy Felix [ORNL; Goddard, James K [ORNL; Habte Ghebretatios, Frezghi [ORNL; Karnowski, Thomas Paul [ORNL

2008-01-01T23:59:59.000Z

82

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

83

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

84

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.

85

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.

86

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

87

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

88

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

89

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

90

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

91

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

92

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

93

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

94

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

95

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

96

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

97

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

98

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

99

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

100

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

102

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

103

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

104

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

105

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

106

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

107

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

108

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

109

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

110

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

111

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

112

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

113

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

114

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

115

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

116

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

117

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

118

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

119

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

120

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

122

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

123

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

124

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

125

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

126

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

127

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

128

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

129

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

130

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

131

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

132

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

133

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

134

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

135

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

136

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

137

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

138

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

139

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

140

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

142

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

143

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

144

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

145

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

146

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

147

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

148

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

149

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

150

Observational Constraints on Cosmological Models with the Updated Long Gamma-Ray Bursts  

E-Print Network (OSTI)

In the present work, by the help of the newly released Union2 compilation which consists of 557 Type Ia supernovae (SNIa), we calibrate 109 long Gamma-Ray Bursts (GRBs) with the well-known Amati relation, using the cosmology-independent calibration method proposed by Liang {\\it et al.}. We have obtained 59 calibrated high-redshift GRBs which can be used to constrain cosmological models without the circularity problem (we call them ``Hymnium'' GRBs sample for convenience). Then, we consider the joint constraints on 7 cosmological models from the latest observational data, namely, the combination of 557 Union2 SNIa dataset, 59 calibrated Hymnium GRBs dataset (obtained in this work), the shift parameter $R$ from the WMAP 7-year data, and the distance parameter $A$ of the measurement of the baryon acoustic oscillation (BAO) peak in the distribution of SDSS luminous red galaxies. We also briefly consider the comparison of these 7 cosmological models.

Hao Wei

2010-04-28T23:59:59.000Z

151

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

152

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

153

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

154

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

155

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

156

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

157

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

158

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

159

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

160

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

162

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

163

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

164

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

165

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

166

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

167

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

168

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

169

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.

170

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

171

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

172

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

173

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

174

Calibration Facilities | Department of Energy  

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

Calibration Facilities Calibration Facilities Calibration Facilities Calibration Facilities Calibration Facilities Calibration Facilities Calibration Facilities DOE supports the development, standardization, and maintenance of calibration facilities for environmental radiation sensors. Radiation standards at the facilities are primarily used to calibrate portable surface gamma-ray survey meters and borehole logging instruments used for uranium and other mineral exploration and remedial action measurements. Standards for calibrating borehole fission neutron devices are also available, but are used infrequently. Radiation standards are constructed of concrete with elevated, uniform concentrations of naturally occurring potassium, uranium, and/or thorium. Pad standards have large, flat surfaces suitable for calibration

175

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

176

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

177

(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

178

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

179

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

180

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

182

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

183

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

184

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

185

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

186

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

187

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

188

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

189

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

190

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

191

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

192

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

193

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

194

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

195

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

196

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

197

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

198

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

199

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

200

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

202

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

203

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

204

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

205

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

206

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

207

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

208

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

209

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

210

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

211

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

212

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

213

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

214

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

215

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

216

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

217

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

218

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

219

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

220

The drive system of the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope  

E-Print Network (OSTI)

The MAGIC telescope is an imaging atmospheric Cherenkov telescope, designed to observe very high energy gamma-rays while achieving a low energy threshold. One of the key science goals is fast follow-up of the enigmatic and short lived gamma-ray bursts. The drive system for the telescope has to meet two basic demands: (1) During normal observations, the 72-ton telescope has to be positioned accurately, and has to track a given sky position with high precision at a typical rotational speed in the order of one revolution per day. (2) For successfully observing GRB prompt emission and afterglows, it has to be powerful enough to position to an arbitrary point on the sky within a few ten seconds and commence normal tracking immediately thereafter. To meet these requirements, the implementation and realization of the drive system relies strongly on standard industry components to ensure robustness and reliability. In this paper, we describe the mechanical setup, the drive control and the calibration of the pointing, as well as present measurements of the accuracy of the system. We show that the drive system is mechanically able to operate the motors with an accuracy even better than the feedback values from the axes. In the context of future projects, envisaging telescope arrays comprising about 100 individual instruments, the robustness and scalability of the concept is emphasized.

T. Bretz; D. Dorner; R. M. Wagner; P. Sawallisch

2008-10-27T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

222

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

223

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

224

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

225

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

226

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

227

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

228

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

229

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

230

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

231

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

232

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.

233

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

234

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

235

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.

236

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

237

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

238

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

239

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.

240

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.

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


241

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

242

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

243

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

244

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

245

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

246

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

247

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

248

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

249

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

250

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

251

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

252

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

253

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

254

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

255

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

256

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

257

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

258

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

259

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

260

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


261

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

262

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

263

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

264

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

265

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

266

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

267

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

268

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

269

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

270

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

271

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

272

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

273

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

274

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

275

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

276

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

277

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

278

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

279

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

280

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

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

282

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

283

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

284

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

285

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

286

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

287

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

288

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

289

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

290

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

291

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

292

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

293

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

294

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

295

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

296

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

297

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

298

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

299

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

300

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...

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


301

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

302

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

303

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

304

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

305

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

306

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

307

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

308

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

309

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

310

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

311

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

312

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

313

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

314

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

315

Analysis of gamma-ray dosimetry experiments in the zero power MINERVE facility  

Science Conference Proceedings (OSTI)

The objective of this study is to develop nuclear heating measurement methods in zero power experimental reactors. These developments contribute to the qualification of photonics calculation schemes for the assessment of gamma heating in the future Jules Horowitz Material Testing Reactor. This paper presents the analysis of thermoluminescent detector (TLD) experiments in the UO{sub 2} core of the MINERVE Research Reactor at the French Alternative Energies and Atomic Energy Commission center in Cadarache. The experimental sources of uncertainty in the gamma dose have been reduced by improving the measurement conditions and the repeatability of the calibration step for each individual TLD. The interpretation of these measurements needs to take into account the calculation of cavity correction factors related to calibration and irradiation configurations, as well as neutron correction calculations. These calculations are based on Monte Carlo simulations of neutron-gamma and gamma-electron transport coupled particles. The comparison between calculated and measured integral gamma-ray absorbed doses in the aluminum material surrounding the TLD shows that calculations slightly overestimate the measurement, with a calculated versus experimental ratio equal to 1.04 {+-} 5.7 % (k=2). (authors)

Amharrak, H.; Di Salvo, J.; Lyoussi, A.; Roche, A.; Masson-Fauchier, M.; Bosq, J. C. [CEA, DEN, DER, F-13108 Saint-Paul-lez-Durance (France); Carette, M. [Aix-Marseille Univ., LCP UMR 6264, 13397, Marseille (France)

2011-07-01T23:59:59.000Z

316

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.

317

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

318

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.

Falcone, A D; Baring, M G; Blandford, R; Buckley, J; Connaughton, V; Coppi, P; Dermer, C; Dingus, B; Fryer, C; Gehrels, N; Granot, J; Horan, D; Katz, J I; Kühn, K; Mészáros, P; Norris, J; Parkinson, P Saz; Peér, A; Ramirez-Ruiz, E; Razzaque, S; Wang, X Y; Zhang, B

2008-01-01T23:59:59.000Z

319

Waves on Noncommutative Spacetime and Gamma-Ray Bursts  

E-Print Network (OSTI)

Quantum group Fourier transform methods are applied to the study of processes on noncommutative Minkowski spacetime $[x^i,t]=\\imath\\lambda x^i$. A natural wave equation is derived and the associated phenomena of {\\it in vacuo} dispersion are discussed. Assuming the deformation scale $\\lambda$ is of the order of the Planck length one finds that the dispersion effects are large enough to be tested in experimental investigations of astrophysical phenomena such as gamma-ray bursts. We also outline a new approach to the construction of field theories on the noncommutative spacetime, with the noncommutativity equivalent under Fourier transform to non-Abelianness of the `addition law' for momentum in Feynman diagrams. We argue that CPT violation effects of the type testable using the sensitive neutral-kaon system are to be expected in such a theory.

Giovanni Amelino-Camelia; Shahn Majid

1999-07-14T23:59:59.000Z

320

Gamma-Ray Bursts - a Primer For Relativists  

E-Print Network (OSTI)

Gamma-Ray Bursts (GRBs) - short bursts of 100-1MeV photons arriving from random directions in the sky are probably the most relativistic objects discovered so far. Still, somehow they did not attract the attention of the relativistic community. In this short review I discuss briefly GRB observations and show that they lead us to the fireball model - GRBs involve macroscopic relativistic motion with Lorentz factors of a few hundred or more. I show that GRB sources involve, most likely, new born black holes, and their progenitors are Supernovae or neutron star mergers. I show that both GRB progenitors and the process of GRB itself produce gravitational radiation and I consider the possibility of detecting this emission. Finally I show that GRBs could serve as cosmological indicators that could teach us about the high redshift ($z \\approx 5-15$) dark ages of the universe.

Tsvi Piran

2002-05-12T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

Quantifying the Luminosity Evolution in Gamma-ray Bursts  

E-Print Network (OSTI)

We estimate the luminosity evolution and formation rate for over 900 GRBs by using redshift and luminosity data calculated by Band, Norris, $&$ Bonnell (2004) via the lag-luminosity correlation. By applying maximum likelihood techniques, we are able to infer the true distribution of the parent GRB population's luminosity function and density distributions in a way that accounts for detector selection effects. We find that after accounting for data truncation, there still exists a significant correlation between the average luminosity and redshift, indicating that distant GRBs are on average more luminous than nearby counterparts. This is consistent with previous studies showing strong source evolution and also recent observations of under luminous nearby GRBs. We find no evidence for beaming angle evolution in the current sample of GRBs with known redshift, suggesting that this increase in luminosity can not be due to an evolution of the collimation of gamma-ray emission. The resulting luminosity function...

Kocevski, D; Kocevski, Daniel; Liang, Edison

2006-01-01T23:59:59.000Z

322

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

323

GRAVITATIONAL WAVES OF JET PRECESSION IN GAMMA-RAY BURSTS  

SciTech Connect

The physical nature of gamma-ray bursts (GRBs) is believed to involve an ultra-relativistic jet. The observed complex structure of light curves motivates the idea of jet precession. In this work, we study the gravitational waves of jet precession based on neutrino-dominated accretion disks around black holes, which may account for the central engine of GRBs. In our model, the jet and the inner part of the disk may precess along with the black hole, which is driven by the outer part of the disk. Gravitational waves are therefore expected to be significant from this black-hole-inner-disk precession system. By comparing our numerical results with the sensitivity of some detectors, we find that it is possible for DECIGO and BBO to detect such gravitational waves, particularly for GRBs in the Local Group.

Sun Mouyuan; Liu Tong; Gu Weimin; Lu Jufu, E-mail: tongliu@xmu.edu.cn [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)

2012-06-10T23:59:59.000Z

324

Finding (Or Not) New Gamma-Ray Pulsars with GLAST  

SciTech Connect

Young energetic pulsars will likely be the largest class of Galactic sources observed by GLAST, with many hundreds detected. Many will be unknown as radio pulsars, making pulsation detection dependent on radio and/or x-ray observations or on blind periodicity searches of the gamma-rays. Estimates for the number of pulsars GLAST will detect in blind searches have ranged from tens to many hundreds. I argue that the number will be near the low end of this range, partly due to observations being made in a scanning as opposed to a pointing mode. This paper briefly reviews how blind pulsar searches will be conducted using GLAST, what limits these searches, and how the computations and statistics scale with various parameters.

Ransom, Scott M.; /NRAO, Charlottesville

2011-11-29T23:59:59.000Z

325

Polarized Gravitational Waves from Gamma-Ray Bursts  

E-Print Network (OSTI)

Significant gravitational wave emission is expected from gamma-ray bursts arising from compact stellar mergers, and possibly also from bursts associated with fast-rotating massive stellar core collapses. These models have in common a high angular rotation rate, and observations provide evidence for jet collimation of the photon emission, with properties depending on the polar angle, which may also be of relevance for X-ray flashes. Here we consider the gravitational wave emission and its polarization as a function of angle which is expected from such sources. We discuss possible correlations between the burst photon luminosity, or the delay between gravitational wave bursts and X-ray flashes, and the polarization degree of the gravitational waves.

Shiho Kobayashi; Peter Meszaros

2002-12-25T23:59:59.000Z

326

Cosmic Gamma-Ray Bursts The Remaining Mysteries  

E-Print Network (OSTI)

To anyone who has read a scientific journal or even a newspaper in the last six months, it might appear that cosmic gamma-ray bursts hold no more mysteries: they are cosmological, and possibly the most powerful explosions in the Universe. In fact, however, bursts remain mysterious in many ways. There is no general agreement upon the nature of the event which releases the initial energy. One burst at least appears to strain the energy budget of the merging neutron star model. There is evidence that another recent event may have come from a nearby supernova. Finally, while the number count statistics clearly show a strong deviation from the -3/2 power law expected for a Euclidean, homogeneous distribution, the distributions of some classes of bursts appear to follow a -3/2 power law rather closely. The recent data on bursts is reviewed, some of the mysteries discussed, and future experiments are outlined.

Hurley, K

1998-01-01T23:59:59.000Z

327

Compact Gamma-ray Source Technology Development Study  

SciTech Connect

This study focuses on the applicability of current accelerator and laser technologies to the construction of compact, narrow bandwidth, gamma-ray sources for DHS missions in illicit materials detection. It also identifies research and development areas in which advancement will directly benefit these light sources. In particular, we review the physics of Compton scattering based light sources and emphasize the source properties most important to Nuclear Resonance Fluorescence (NRF) applications of interest. The influences of laser and electron beam properties on the light source are examined in order to evaluate the utility of different technologies for this application. Applicable bulk and fiber-based laser systems and laser recirculation technologies are discussed and Radio Frequency (RF) Linear Accelerator (linac) technologies are examined to determine the optimal frequency and pulse formats achievable.

Anderson, S G; Gibson, D J; Rusnak, B

2009-09-25T23:59:59.000Z

328

Testing Mass Varying Neutrino With Short Gamma Ray Burst  

E-Print Network (OSTI)

In this paper we study the possibility of probing for the absolute neutrino mass and its variation with short Gamma Ray Burst (GRB). We have calculated the flight time difference between a massive neutrino and a photon in two different approaches to mass varying neutrinos. Firstly we parametrize the neutrino mass as a function of redshift in a model independent way, then we consider two specific models where the neutrino mass varies during the evolution of the Quintessence fields. Our calculations show in general the value of the time delay is changed substantially relative to a constant neutrino mass. Furthermore our numerical results show that the flight time delay in these models is expected to be larger than the duration time of the short GRB, which opens a possibility of testing the scenario of mass varying neutrino with the short GRB.

Hong Li; Zigao Dai; Xinmin Zhang

2004-11-17T23:59:59.000Z

329

Gravitational Wave Memory of Gamma-Ray Burst Jets  

E-Print Network (OSTI)

Gamma-Ray Bursts (GRBs) are now considered as relativistic jets. We analyze the gravitational waves from the acceleration stage of the GRB jets. We show that (i) the point mass approximation is not appropriate if the opening half-angle of the jet is larger than the inverse of the Lorentz factor of the jet, (ii) the gravitational waveform has many step function like jumps, and (iii) the practical DECIGO and BBO may detect such an event if the GRBs occur in Local group of galaxy. We found that the light curve of GRBs and the gravitational waveform are anti-correlated so that the detection of the gravitational wave is indispensable to determine the structure of GRB jets.

Norichika Sago; Kunihito Ioka; Takashi Nakamura; Ryo Yamazaki

2004-05-13T23:59:59.000Z

330

Study of Lorentz violation in INTEGRAL Gamma-Ray Bursts  

E-Print Network (OSTI)

We search for possible time lags caused by quantum gravitational (QG) effects using gamma-ray bursts (GRBs) detected by INTEGRAL. The advantage of this satellite is that we have at our disposal the energy and arrival time of every detected single photon, which enhances the precision of the time resolution. We present a new method for seeking time lags in unbinned data using a maximum likelihood method and support our conclusions with Monte Carlo simulations. The analysis of the data yields a mass scale well below the Planck mass whose value may however increase if better statistics of GRBs were available. Furthermore, we disagree with previous studies in which a non-monotonic function of the redshift was used to perform a linear fit.

Raphael Lamon; Nicolas Produit; Frank Steiner

2007-06-27T23:59:59.000Z

331

General Relativistic Binary Merger Simulations and Short Gamma Ray Bursts  

E-Print Network (OSTI)

The recent localization of some short-hard gamma ray bursts (GRBs) in galaxies with low star formation rates has lent support to the suggestion that these events result from compact object binary mergers. We discuss how new simulations in general relativity are helping to identify the central engine of short-hard GRBs. Motivated by our latest relativistic black hole-neutron star merger calculations, we discuss a scenario in which these events may trigger short-hard GRBs, and compare this model to competing relativistic models involving binary neutron star mergers and the delayed collapse of hypermassive neutron stars. Distinguishing features of these models may help guide future GRB and gravitational wave observations to identify the nature of the sources.

Joshua A. Faber; Thomas W. Baumgarte; Stuart L. Shapiro; Keisuke Taniguchi

2006-03-10T23:59:59.000Z

332

Study of galactic gamma ray sources with Milagro Jordan A. Goodman for the Milagro Collaboration  

E-Print Network (OSTI)

Study of galactic gamma ray sources with Milagro Jordan A. Goodman for the Milagro Collaboration. This factor of ~2 increase in sensitivity (as shown in figure 1) has dramatically changed our view of the high-energy Galactic gamma-ray emission at TeV energies, including the detection of the Cygnus Region at high

California at Santa Cruz, University of

333

Title of dissertation: A SEARCH FOR BURSTS OF VERY HIGH ENERGY GAMMA RAYS  

E-Print Network (OSTI)

ABSTRACT Title of dissertation: A SEARCH FOR BURSTS OF VERY HIGH ENERGY GAMMA RAYS WITH MILAGRO Vlasios Vasileiou, Doctor of Philosophy, 2008 Dissertation directed by: Professor Jordan A. Goodman by cosmic gamma rays of energies E 100 GeV . The effective area of Milagro peaks at energies E 10 Te

California at Santa Cruz, University of

334

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

335

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

336

Swift Pointing and Gravitational-Wave Bursts from Gamma-Ray Burst Events  

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. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. This 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 bursts 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

2003-04-23T23:59:59.000Z

337

HETE, the High Energy Transient Explorer : unlocking the mysteries of gamma ray bursts  

E-Print Network (OSTI)

The High Energy Transient Explorer (HETE), was built primarily at MIT and launched in October 2000 with the goal of studying Gamma Ray Bursts (GRBs) at X-ray and gamma-ray energies. A suite of instruments aboard HETE provide ...

Monnelly, Glen Pickslay, 1973-

2002-01-01T23:59:59.000Z

338

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

E-Print Network (OSTI)

Prompt and Delayed High­Energy Emission from Cosmological Gamma­Ray Bursts Markus B¨ottcher a, Washington, DC 20375­5352 Abstract In the cosmological blast­wave model for gamma ray bursts (GRBs), high if they are indeed associated with star­forming regions. 3 Comparison with Gamma Rays from Hadronic Processes

California at Santa Cruz, University of

339

Neutrinos from gamma-ray bursts as a tool to explore quantum-gravity-induced  

E-Print Network (OSTI)

LETTERS Neutrinos from gamma-ray bursts as a tool to explore quantum-gravity-induced Lorentz energy scale. According to existing models, gamma-ray bursts (GRBs) are accompanied by very high from the same direction as a GRB, months after the burst, would be statistically significant and imply

Loss, Daniel

340

Short gamma-ray bursts from binary neutron star mergers in globular clusters  

E-Print Network (OSTI)

ARTICLES Short gamma-ray bursts from binary neutron star mergers in globular clusters JONATHAN@cfa.harvard.edu Published online: 29 January 2006; doi:10.1038/nphys214 Observations by the Swift gamma-ray-burst (GRB, the so-called `long' GRBs (>2-200 s) were located by coded aperture imaging of their hard X-ray emission

Loss, Daniel

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

Neutron interrogation system using high gamma ray signature to detect contraband special nuclear materials in cargo  

DOE Patents (OSTI)

A system for inspecting cargo for the presence of special nuclear material. The cargo is irradiated with neutrons. The neutrons produce fission products in the special nuclear material which generate gamma rays. The gamma rays are detecting indicating the presence of the special nuclear material.

Slaughter, Dennis R. (Oakland, CA); Pohl, Bertram A. (Berkeley, CA); Dougan, Arden D. (San Ramon, CA); Bernstein, Adam (Palo Alto, CA); Prussin, Stanley G. (Kensington, CA); Norman, Eric B. (Oakland, CA)

2008-04-15T23:59:59.000Z

342

Toward finding gravitational-wave signals from progenitors of short hard gamma-ray bursts and orphaned afterglows  

E-Print Network (OSTI)

With multiple observatories and missions being planned for detecting orphaned afterglows associated with gamma-ray bursts (GRBs) we emphasize the importance of developing data analysis strategies for searching their possible counterpart signals in the data of gravitational wave (GW) detectors in the advanced detector era. This is especially attractive since short hard gamma-ray bursts (SGRBs) may have compact binary coalescences involving neutron stars (CBCNSs) as their progenitors, which emit gravitational waves. Joint electromagnetic (EM) and GW observations of these objects will enrich our understanding of their beaming, energetics, galactic environment, and shed light on a host of other outstanding questions related to them. Here we recognize some of the astrophysical factors that determine what fraction of CBCNS sources can generate orphaned afterglows. Pipelines already exist that target the sky-position and time of occurrence of SGRBs, known from EM observations, to search for their counterparts in GW detector data. Modifying them to analyze extended periods of time in the GW data in the past of the afterglow detection, while targeting a single sky-position, can search for GWs from the common progenitor. We assess the improvement in GW detectability to be had from utilizing the sky-position information. We also propose a method for improving the detection efficiency of targeted searches of GW signals from the putative CBCNS sources of afterglows and short gamma ray bursts in the presence of errors in detector calibration or CBCNS waveform models used in the search. The improvement arises from searching in a wider patch of the sky even when the sky-position is known accurately from EM observations and utilizes the covariance of the errors in waveform parameters with those in the sky position.

Shaon Ghosh; Sukanta Bose

2013-08-28T23:59:59.000Z

343

Direction-Sensitive Hand-Held Gamma-Ray Spectrometer  

SciTech Connect

A novel, light-weight, hand-held gamma-ray detector with directional sensitivity is being designed. The detector uses a set of multiple rings around two cylindrical surfaces, which provides precise location of two interaction points on two concentric cylindrical planes, wherefrom the source location can be traced back by back projection and/or Compton imaging technique. The detectors are 2.0 × 2.0 mm europium-doped strontium iodide (SrI2:Eu2+) crystals, whose light output has been measured to exceed 120,000 photons/MeV, making it one of the brightest scintillators in existence. The crystal’s energy resolution, less than 3% at 662 keV, is also excellent, and the response is highly linear over a wide range of gamma-ray energies. The emission of SrI2:Eu2+ is well matched to both photo-multiplier tubes and blue-enhanced silicon photodiodes. The solid-state photomultipliers used in this design (each 2.0 × 2.0 mm) are arrays of active pixel sensors (avalanche photodiodes driven beyond their breakdown voltage in reverse bias); each pixel acts as a binary photon detector, and their summed output is an analog representation of the total photon energy, while the individual pixel accurately defines the point of interaction. A simple back-projection algorithm involving cone-surface mapping is being modeled. The back projection for an event cone is a conical surface defining the possible location of the source. The cone axis is the straight line passing through the first and second interaction points.

Mukhopadhyay, S.

2012-10-04T23:59:59.000Z

344

Propagation of Neutrinos through Magnetized Gamma-Ray Burst Fireball  

E-Print Network (OSTI)

The neutrino self-energy is calculated in a weakly magnetized plasma consists of electrons, protons, neutrons and their anti-particles and using this we have calculated the neutrino effective potential up to order $M^{-4}_W$. In the absence of magnetic field it reduces to the known result. We have also calculated explicitly the effective potentials for different backgrounds which may be helpful in different environments. By considering the mixing of three active neutrinos in the medium with the magnetic field we have derived the survival and conversion probabilities of neutrinos from one flavor to another and also the resonance condition is derived. As an application of the above, we considered the dense and relativistic plasma of the Gamma-Ray Bursts fireball through which neutrinos of 5-30 MeV can propagate and depending on the fireball parameters they may oscillate resonantly or non-resonantly from one flavor to another. These MeV neutrinos are produced due to stellar collapse or merger events which trigger the Gamma-Ray Burst. The fireball itself also produces MeV neutrinos due to electron positron annihilation, inverse beta decay and nucleonic bremsstrahlung. Using the three neutrino mixing and considering the best fit values of the neutrino parameters, we found that electron neutrinos are hard to oscillate to another flavors. On the other hand, the muon neutrinos and the tau neutrinos oscillate with equal probability to one another, which depends on the neutrino energy, temperature and size of the fireball. Comparison of oscillation probabilities with and without magnetic field shows that, they depend on the neutrino energy and also on the size of the fireball. By using the resonance condition, we have also estimated the resonance length of the propagating neutrinos as well as the baryon content of the fireball.

Sarira Sahu; Nissim Fraija; Yong-Yeon Keum

2009-09-16T23:59:59.000Z

345

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

346

Using gamma-ray emission to measure areal density of ICF capsules  

SciTech Connect

Fusion neutrons streaming from a burning ICF capsule generate gamma rays via nuclear inelastic scattering in the ablator of the capsule. The intensity of gamma-ray emission is proportional to the product of the ablator areal density ('{rho}R') and the yield of fusion neutrons, so by detecting the gamma rays we can infer the ablator areal density, provided we also have a measurement of the capsule's total neutron yield. In plastic-shell capsules, for example, {sup 12}C nuclei emit gamma rays at 4.44 MeV after excitation by 14.1-MeV neutrons from D+T fusion. These gamma rays can be measured by the Gamma Reaction History (GRH) experiment being built at the National Ignition Facility (NIF). A linear error analysis indicates the chief sources of uncertainty in inferred areal density.

Hoffman, Nelson M [Los Alamos National Laboratory; Wilson, Douglas C [Los Alamos National Laboratory; Hermann, Hans W [Los Alamos National Laboratory; Young, Carlton S [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

347

Precision linac and laser technologies for nuclear photonics gamma-ray sources  

SciTech Connect

Tunable, high precision gamma-ray sources are under development to enable nuclear photonics, an emerging field of research. This paper focuses on the technological and theoretical challenges related to precision Compton scattering gamma-ray sources. In this scheme, incident laser photons are scattered and Doppler upshifted by a high brightness electron beam to generate tunable and highly collimated gamma-ray pulses. The electron and laser beam parameters can be optimized to achieve the spectral brightness and narrow bandwidth required by nuclear photonics applications. A description of the design of the next generation precision gamma-ray source currently under construction at Lawrence Livermore National Laboratory is presented, along with the underlying motivations. Within this context, high-gradient X-band technology, used in conjunction with fiber-based photocathode drive laser and diode pumped solid-state interaction laser technologies, will be shown to offer optimal performance for high gamma-ray spectral flux, narrow bandwidth applications.

Albert, F.; Hartemann, F. V.; Anderson, S. G.; Cross, R. R.; Gibson, D. J.; Hall, J.; Marsh, R. A.; Messerly, M.; Wu, S. S.; Siders, C. W.; Barty, C. P. J. [Lawrence Livermore National Laboratory, NIF and Photon Science, 7000 East Avenue, Livermore, California 94550 (United States)

2012-05-15T23:59:59.000Z

348

Short Gamma Ray Bursts as possible electromagnetic counterpart of coalescing binary systems  

E-Print Network (OSTI)

Coalescing binary systems, consisting of two collapsed objects, are among the most promising sources of high frequency gravitational waves signals detectable, in principle, by ground-based interferometers. Binary systems of Neutron Star or Black Hole/Neutron Star mergers should also give rise to short Gamma Ray Bursts, a subclass of Gamma Ray Bursts. Short-hard-Gamma Ray Bursts might thus provide a powerful way to infer the merger rate of two-collapsed object binaries. Under the hypothesis that most short Gamma Ray Bursts originate from binaries of Neutron Star or Black Hole/Neutron Star mergers, we outline here the possibility to associate short Gamma Ray Bursts as electromagnetic counterpart of coalescing binary systems.

S. Capozziello; M. De Laurentis; I. De Martino; M. Formisano

2010-04-27T23:59:59.000Z

349

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...

350

A Search for Muon Neutrinos from Gamma-Ray Bursts wih the IceCube 22-String Detector.  

E-Print Network (OSTI)

??Two searches are conducted for muon neutrinos from Gamma-Ray Bursts (GRBs) using the IceCube detector. Gamma-Ray Bursts are brief and transient emissions of keV/MeV radiation… (more)

Roth, A Philip

2009-01-01T23:59:59.000Z

351

SWIFT PANCHROMATIC OBSERVATIONS OF THE BRIGHT GAMMA-RAY BURST GRB 050525a A. J. Blustin,1  

E-Print Network (OSTI)

SWIFT PANCHROMATIC OBSERVATIONS OF THE BRIGHT GAMMA-RAY BURST GRB 050525a A. J. Blustin,1 D. Band,2 ABSTRACT The bright gamma-ray burst GRB 050525a has been detected with the Swift observatory, providing. This jet break time combined with the total gamma-ray energy of the burst constrains the opening angle

Zhang, Bing

352

ON THE KINETIC ENERGY AND RADIATIVE EFFICIENCY OF GAMMA-RAY BURSTS Nicole M. Lloyd-Ronning1  

E-Print Network (OSTI)

ON THE KINETIC ENERGY AND RADIATIVE EFFICIENCY OF GAMMA-RAY BURSTS Nicole M. Lloyd-Ronning1 of 17 gamma-ray bursts (GRBs) during the afterglow phase and ac- counting for radiative losses, we the implications of these results for the GRB radiation and jet models. Subject headinggs: gamma rays: bursts

Zhang, Bing

353

Gehrels_Answers 311.pdf Student questions: Neil Gehrels colloquium on "Gamma Ray Bursts and the Birth of Black  

E-Print Network (OSTI)

gamma repeaters, or gamma-ray bursts for which optical or ra- dio counterparts are found. In its first of HETE, the two principal GRB detectors close to Earth were the BeppoSAX Gamma- Ray Burst Moni- tor (GRBM aboard HETE-II has been successfully integrated into the Third Interplanetary Network (IPN) of gamma-ray

Rhoads, James

354

The gamma-ray burst monitor for Lobster-ISS L. Amati a,*, F. Frontera a,b  

E-Print Network (OSTI)

The gamma-ray burst monitor for Lobster-ISS L. Amati a,*, F. Frontera a,b , N. Auricchio a , E telescope is flanked by a Gamma Ray Burst Monitor, with the minimum requirement of recognizing true GRBs. Published by Elsevier Ltd. All rights reserved. Keywords: Gamma-rays: bursts; X-rays: transients

Bogliolo, Alessandro

355

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

356

30TH INTERNATIONAL COSMIC RAY CONFERENCE Search for Gamma Ray Bursts using the single particle technique at the Pierre Auger  

E-Print Network (OSTI)

30TH INTERNATIONAL COSMIC RAY CONFERENCE Search for Gamma Ray Bursts using the single particle by satellites. Introduction Since their discovery at the end of the 60s[1], Gamma Ray Bursts (GRB) have been of high in- terest to astrophysics. A GRB is characterised by a sudden emission of gamma rays during

Hörandel, Jörg R.

357

Title of Dissertation: A Search for Short Duration Very High Energy Emission from Gamma-Ray Bursts  

E-Print Network (OSTI)

of GRBs. #12;A Search for Short Duration Very High Energy Emission from Gamma-Ray Bursts by David Noyes Gamma-Ray Bursts 1 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 60 3 The Gamma-Ray Burst Search 64 3.1 Introduction

California at Santa Cruz, University of

358

Magnetic Fields in Gamma-Ray Bursts: A Short Racah Institute for Physics, The Hebrew University, Jerusalem, 91904 Israel  

E-Print Network (OSTI)

Magnetic Fields in Gamma-Ray Bursts: A Short Overview Tsvi Piran Racah Institute for Physics Abstract. Magnetic fields play a crucial role in the physics of Gamma-Ray Bursts (GRBs). Strong thirty years, after the discovery of Gamma-Ray bursts (GRBs) we have now a reasonable GRB model

Jensen, Grant J.

359

JET BREAKS IN SHORT GAMMA-RAY BURSTS. I. THE UNCOLLIMATED AFTERGLOW OF GRB 050724 Dirk Grupe,1  

E-Print Network (OSTI)

JET BREAKS IN SHORT GAMMA-RAY BURSTS. I. THE UNCOLLIMATED AFTERGLOW OF GRB 050724 Dirk Grupe,1 the results of the Chandra observations of the Swift-discovered short gamma-ray burst GRB 050724. Chandra corrected energy of GRB 050724 is at least 4 ; 1049 ergs. Subject headinggs: gamma rays: bursts -- X-rays

Zhang, Bing

360

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

Note: This page contains sample records for the topic "gamma-ray calibration blocks" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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361

Real-Time Optical Flux Limits From Gamma-Ray Bursts Measured By The GROCSE Experiment  

E-Print Network (OSTI)

The Gamma-Ray Optical Counterpart Search Experiment (GROCSE) presents new experimental upper limits on the optical flux from gamma-ray bursts (GRBs). Our experiment consisted of a fully-automated very wide-field opto-electronic detection system that imaged locations of GRBs within a few seconds of receiving trigger signals provided by BATSE’s real-time burst coordinate distribution network (BACODINE). The experiment acquired 3800 observing hours, recording 22 gamma-ray burst triggers within ?30 s of the start of the burst event. Some of these bursts were imaged while gamma-ray radiation was being detected by BATSE. We identified no optical counterparts associated with gamma-ray bursts amongst these events at the mV ? 7.0 to 8.5 sensitivity level. We find the ratio of the upper limit to the V-band optical flux, F?, to the gamma-ray fluence, ??, from these data to be 2 × 10?18 gamma rays: bursts – 3 – 1.

H. S. Park; E. Ables; S. D. Barthelmy; R. M. Bionta; P. S. Butterworth; T. L. Cline; D. H. Ferguson; G. J. Fishman; N. Gehrels; K. Hurley; C. Kouveliotou; B. C. Lee; C. A. Meegan; L. L. Ott; E. L. Parker Received Accepted

1997-01-01T23:59:59.000Z

362

Relativistic Conic Beams and Spatial Distribution of Gamma-Ray Bursts  

E-Print Network (OSTI)

We study the statistics of gamma-ray bursts, assuming that gamma-ray bursts are cosmological and they are beamed in the form of a conical jet with a large bulk Lorentz factor $\\sim 100$. In such a conic beam, the relativistic ejecta may have a spatial variation in the bulk Lorentz factor and the density distribution of gamma-ray emitting jet material. An apparent luminosity function arises because the axis of the cone is randomly oriented with respect to the observer's line of sight. The width and the shape of the luminosity function are determined by the ratio of the beam opening angle of the conical jet to the inverse of the bulk Lorentz factor, when the bulk Lorentz factor and the jet material density is uniform on the photon emitting jet surface. We calculate effects of spatial variation of the Lorentz factor and the spatial density fluctuations within the cone on the luminosity function and the statistics of gamma-ray bursts. In particular, we focus on the redshift distribution of the observed gamma-ray bursts. The maximum distance to and the average redshift of the gamma-ray bursts are strongly affected by the beaming-induced luminosity function. The bursts with the angle-dependent Lorentz factor which peaks at the center of the cone have substantially higher average gamma-ray burst redshifts. When both the jet material density and the Lorentz factor are inhomogeneous in the conical beam, the average redshift of the bursts could be 5 times higher than that of the case in which relativistic jet is completely homogeneous and structureless. Even the simplest models for the gamma-ray burst jets and their apparent luminosity distributions have a significant effect on the redshift distribution of the gamma-ray bursts.

Heon-Young Chang; Insu Yi

2000-05-15T23:59:59.000Z

363

Gamma-ray decay schemes for $sup 93$Kr, $sup 93$Rb, and $sup 93$Sr  

SciTech Connect

A study of the gamma-ray de-excitation following the beta decays of $sup 93$Kr, $sup 93$Rb, and $sup 93$Sr using the TRISTAN on-line separator facility is reported. Gamma-ray singles and gamma-gamma coincidence measurements were made using Ge(Li) detectors. Of the 162 gamma rays observed in the decay of $sup 93$Sr, 143, representing more than 99 percent of the total gamma-ray intensity observed, were placed in a level scheme containing 36 levels. For the decay of $sup 93$Rb, 243 gamma rays were observed, of which 231 are placed in a level scheme consisting of 74 levels. This again represents a placement of over 99 percent of the total gamma-ray intensity measured. In the case of the $sup 93$Kr decay approximately 98.5 percent of the observed gamma-ray intensity has been accounted for by the proposed level scheme. This results from the placement of 203 of the 217 gamma rays assigned to this decay in a level scheme comprising 56 levels. Beta-branching for these decays were determined from transition intensity balances. Spin and parity assignments were proposed, whenever possible, on the basis of gamma-ray transition probabilities and deduced log ft values. A comparison is made with the available reaction data for the $sup 93$Y level scheme. In all cases an attempt has been made to explain some of the levels in terms of the nuclear shell model and decay systematics. 18 figures, 20 tables, 68 references. (auth)

Bischof, C.J.

1976-01-01T23:59:59.000Z

364

On the mechanism of prompt emission of gamma-ray bursts  

E-Print Network (OSTI)

We propose a model in which prompt gamma emission of gamma-ray bursts is the synchrotron radiation of electron-positron plasma in the ordered magnetic field in the direct vicinity of horizon of a young black hole formed in the core collapse of a massive star. This mechanism can naturally explain high degree of polarization of the gamma-ray flux and hard low energy photon spectral index. Interaction of gamma-quanta with ambient matter provides a mechanism of formation of relativistic ejecta which are responsible for the gamma-ray burst afterglows.

Andrey Neronov

2003-11-05T23:59:59.000Z

365

TeV Scale Quantum Gravity and Mirror Supernovae as Sources of Gamma Ray Bursts  

E-Print Network (OSTI)

Mirror matter models have been suggested recently as an explanation of neutrino puzzles and microlensing anomalies. We show that mirror supernovae can be a copious source of energetic gamma rays if one assumes that the quantum gravity scale is in the TeV range. We show that under certain assumptions plausible in the mirror models, the gamma energies could be degraded to the 10 MeV range (and perhaps even further) so as to provide an explanation of observed gamma ray bursts. This mechanism for the origin of the gamma ray bursts has the advantage that it neatly avoids the ``baryon load problem''.

R. N. Mohapatra; S. Nussinov; V. L. Teplitz

1999-09-22T23:59:59.000Z

366

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

367

Emission of Radio Waves in Gamma Ray Bursts and Axionic Boson Stars  

E-Print Network (OSTI)

We point out that the bursts of photons with the energy of the axion mass may appear coincidentally with gamma ray bursts if the gamma ray bursts are caused by collisions between neutron stars and axionic boson stars. In this mechanism, jets are formed in the collisions with large Lorentz factors $\\geq 10^2$. We explain qualitatively time-dependent complex structures of gamma ray bursts as well as the large energy problem. Therefore, with detection of the monochromatic photons we can test the model and determine the axion mass.

Aiichi Iwazaki

1999-08-26T23:59:59.000Z

368

Recent results from the Milagro TeV gamma-ray observatory  

E-Print Network (OSTI)

Milagro is a gamma-ray observatory employing a water Cherenkov detector to observe extensive air showers produced by high-energy particles impacting in the Earth's atmosphere. We discuss the first detection of TeV gamma-rays from the Galactic plane and report the detection of an extended TeV source coincident with the EGRET source 3EG J0520+2556, and the observation of TeV emission from the Cygnus region of our Galaxy. We also summarize the status of our search for Very High Energy (VHE) emission from satellite-triggered Gamma Ray Bursts (GRBs) and discuss plans for the next generation water Cherenkov detector.

Parkinson, P M S

2005-01-01T23:59:59.000Z

369

Toward Ultra Short Gamma Ray Burst Ground Based Detection, SGARFACE status  

E-Print Network (OSTI)

We present the status and motivation of the Short GAmma Ray Front Air Cherenkov Experiment (SGARFACE) which will be operated parallel to standard Very High Energy gamma-ray observations using the Whipple 10m telescope. SGARFACE is sensitive to 100MeV-10GeV gamma-ray bursts with durations ranging from 100ns to 100us providing a fluence sensitivity as low as few $\\rm 1E-9 erg/cm^2. Preliminary data taking started in November 2002.

Stephan LeBohec; Frank Krennrich; Gary Sleege

2002-12-11T23:59:59.000Z

370

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

371

The polarized Gamma-Ray Burst GRB 061122  

E-Print Network (OSTI)

We report on the polarization measure, obtained with IBIS on board INTEGRAL, of the prompt emission of GRB 061122. Over an 8 s interval containing the brightest part of the Gamma-Ray Burst we put a lower limit on its polarization fraction of 60% at 68% c.l. and of 33% at 90% c.l. on the 250-800 keV energy range. We performed late time optical and near infra-red imaging observations of the GRB field using the Telescopio Nazionale Galileo (TNG), and the Canada-France-Hawaii Telescope (CFHT). Our multi-band (ugrizYJHK) photometry allowed us to identify the host galaxy of GRB 061122 and to build its SED. Using a photometric redshift code we fitted these data, and derived the basic properties of the galaxy, including its type and redshift, that we could constrain to the interval [0.57, 2.10] at a 90% c.l., with a best fit value of z=1.33. The polarization measurement in different energy bands, together with the distance determination, allowed us to put the most stringent limit (xi < 3.4x10-16) to date to a poss...

Gotz, D; Fernandez-Soto, A; Laurent, P; Bosnjak, Z

2013-01-01T23:59:59.000Z

372

Neutrinos and Nucleosynthesis in Gamma-Ray Burst Accretion Disks  

E-Print Network (OSTI)

We calculate the nuclear composition of matter in accretion disks surrounding stellar mass black holes as are thought to accompany gamma-ray bursts (GRBs). We follow a mass element in the accretion disk starting at the point of nuclear dissociation and calculate the evolution of the electron fraction due to electron, positron, electron neutrino and electron antineutrino captures. We find that the neutronization of the disk material by electron capture can be reversed by neutrino interactions in the inner regions of disks with accretion rates of 1 M_solar/s and higher. For these cases the inner disk regions are optically thick to neutrinos, and so to estimate the emitted neutrino fluxes we find the surface of last scattering for the neutrinos (the equivalent of the proto-neutron star neutrinosphere) for each optically thick disk model. We also estimate the influence of neutrino interactions on the neutron-to-proton ratio in outflows from GRB accretion disks, and find it can be significant even when the disk is optically thin to neutrinos.

R. Surman; G. C. McLaughlin

2003-07-31T23:59:59.000Z

373

Thermal Emission in Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

We study thermal emission from circumstellar structures heated by gamma-ray burst (GRB) radiation and ejecta and calculate its contribution to GRB optical and X-ray afterglows using the modified radiation hydro-code small STELLA. It is shown that thermal emission originating in heated dense shells around the GRB progenitor star can reproduce X-ray plateaus (like observed in GRB 050904, 070110) as well as deviations from a power law fading observed in optical afterglows of some GRBs (e.g. 020124, 030328, 030429X, 050904). Thermal radiation pressure in the heated circumburst shell dominates the gas pressure, producing rapid expansion of matter similar to supenova-like explosions close to opacity or radiation flux density jumps in the circumburst medium. This phenomenon can be responsible for so-called supernova bumps in optical afterglows of several GRBs. Such a `quasi-supernova' suggests interpretation of the GRB-SN connection which does not directly involve the explosion of the GRB progenitor star.

Badjin, D A

2013-01-01T23:59:59.000Z

374

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

375

The Energy Distribution of Gamma-Ray Bursts  

E-Print Network (OSTI)

The distribution of the apparent total energy emitted by a gamma-ray burst reflects not only the distribution of the energy actually released by the burst engine, but also the distribution of beaming angles. Using the observed energy fluences, the detection thresholds and burst redshifts for three burst samples, I calculate the best-fit parameters for lognormal and power-law distributions of the apparent total energy. Two of the samples include a small number of bursts with spectroscopic redshifts, while the third sample has 220 bursts with redshifts determined by the proposed variability-luminosity correlation. I find different sets of parameter values for the three burst samples. The Bayesian odds ratio cannot distinguish between the two model distribution functions for the two smaller burst samples with spectroscopic redshifts, but does favor the lognormal distribution for the larger sample with variability-derived redshifts. The data do not rule out a distribution with a low energy tail which is currently unobservable. I find that neglecting the burst detection threshold biases the fitted distribution to be narrower with a higher average value than the true distribution; this demonstrates the importance of determining and reporting the effective detection threshold for bursts in a sample.

David L. Band

2001-05-15T23:59:59.000Z

376

REDSHIFT CATALOG FOR SWIFT LONG GAMMA-RAY BURSTS  

Science Conference Proceedings (OSTI)

We present a catalog of the redshifts for most long-duration gamma-ray bursts (GRBs) by Swift from 2004 December 20 to 2008 July 23 (258 bursts in total). All available information is collected, including spectroscopic redshifts, photometric redshift limits, and redshifts calculated from various luminosity relations. Error bars for the redshifts derived from the luminosity relations are asymmetric, with tails extended to the high-redshift end, and this effect is evaluated by looking at the 30% of Swift bursts with spectroscopic redshifts. A simulation is performed to eliminate this asymmetric effect, and the resultant redshift distribution is deconvolved. We test and confirm this simulation on the sample of bursts with known spectroscopic redshifts and then apply it to the 70% of Swift bursts that do not have spectroscopic measures. A final intrinsic redshift distribution is then made for almost all Swift bursts, and the efficiency of the spectroscopic detections is evaluated. The efficiency of spectroscopic redshifts varies from near unity at low redshift to 0.5 at z = 1, to near 0.3 at z = 4, and to 0.1 at z = 6. We also find that the fraction of GRBs with z>5 is {approx}10%, and this fraction is compared with simulations from a cosmological model.

Xiao Limin; Schaefer, Bradley E., E-mail: lxiao1@lsu.edu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States)

2011-04-20T23:59:59.000Z

377

The Molecular Hydrogen Deficit in Gamma-Ray Burst Afterglows  

E-Print Network (OSTI)

Recent analysis of five gamma-ray burst (GRB) afterglow spectra reveal the absence of molecular hydrogen absorption lines, a surprising result in light of their large neutral hydrogen column densities and the detection of H$_2$ in similar, more local star-forming regions like 30 Doradus in the Large Magellanic Cloud (LMC). Observational evidence further indicates that the bulk of the neutral hydrogen column in these sight lines lies 100 pc beyond the progenitor and that H$_2$ was absent prior to the burst, suggesting that direct flux from the star, FUV background fields, or both suppressed its formation. We present one-dimensional radiation hydrodynamical models of GRB host galaxy environments, including self-consistent radiative transfer of both ionizing and Lyman-Werner photons, nine-species primordial chemistry with dust formation of H$_2$, and dust extinction of UV photons. We find that a single GRB progenitor is sufficient to ionize neutral hydrogen to distances of 50 - 100 pc but that a galactic Lyman-Werner background is required to dissociate the molecular hydrogen in the ambient ISM. Intensities of 0.1 - 100 times the Galactic mean are necessary to destroy H$_2$ in the cloud, depending on its density and metallicity. The minimum radii at which neutral hydrogen will be found in afterglow spectra is insensitive to the mass of the progenitor or the initial mass function (IMF) of its cluster, if present.

Daniel Whalen; Jason X. Prochaska; Alexander Heger; Jason Tumlinson

2008-02-06T23:59:59.000Z

378

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

379

MAGNETIZATION DEGREE OF GAMMA-RAY BURST FIREBALLS: NUMERICAL STUDY  

Science Conference Proceedings (OSTI)

The relative strength between forward and reverse shock emission in early gamma-ray burst (GRB) afterglow reflects that of magnetic energy densities in the two shock regions. We numerically show that with the current standard treatment, the fireball magnetization is underestimated by up to two orders of magnitude. This discrepancy is especially large in the sub-relativistic reverse shock regime (i.e., the thin shell and intermediate regime), where most optical flashes were detected. We provide new analytic estimates of the reverse shock emission based on a better shock approximation, which well describe numerical results in the intermediate regime. We show that the reverse shock temperature at the onset of afterglow is constant, ( {Gamma}-bar{sub d}-1){approx}8 Multiplication-Sign 10{sup -2}, when the dimensionless parameter {xi}{sub 0} is more than several. Our approach is applied to case studies of GRB 990123 and 090102, and we find that magnetic fields in the fireballs are even stronger than previously believed. However, these events are still likely to be due to a baryonic jet with {sigma} {approx} 10{sup -3} for GRB 990123 and {approx}3 Multiplication-Sign 10{sup -4} to 3 for GRB 090102.

Harrison, Richard; Kobayashi, Shiho, E-mail: R.M.Harrison@2006.ljmu.ac.uk [Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF (United Kingdom)

2013-08-01T23:59:59.000Z

380

Diversity of the Supernova - Gamma-Ray Burst Connection  

E-Print Network (OSTI)

The connection between the long Gamma Ray Bursts (GRBs) and Type Ic Supernovae (SNe) has revealed interesting diversity. We review the following types of the GRB-SN connection. (1) GRB-SNe: The three SNe all explode with energies much larger than those of typical SNe, thus being called Hypernovae (HNe). They are massive enough for forming black holes. (2) Non-GRB HNe/SNe: Some HNe are not associated with GRBs. (3) XRF-SN: SN 2006aj associated with X-Ray Flash 060218 is dimmer than GRB-SNe and has very weak oxygen lines. Its progenitor mass is estimated to be small enough to form a neutron star rather than a black hole. (4) Non-SN GRB: Two nearby long GRBs were not associated SNe. Such ``dark HNe'' have been predicted in this talk (i.e., just before the discoveries) in order to explain the origin of C-rich (hyper) metal-poor stars. This would be an important confirmation of the Hypernova-First Star connection. We will show our attempt to explain the diversity in a unified manner with the jet-induced explosion model.

K. Nomoto; N. Tominaga; M. Tanaka; K. Maeda; T. Suzuki; J. S. Deng; P. A. Mazzali

2007-02-19T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


381

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

382

Confronting the Hubble Diagram of Gamma-Ray Bursts with Cardassian Cosmology  

E-Print Network (OSTI)

We construct the Hubble diagram (HD) of Gamma-Ray Bursts (GRBs) with redshifts reaching up to $z \\sim 6$, by using five luminosity vs. luminosity indicator relations calibrated with the Cardassian cosmology. This model has a major interesting feature: despite of being matter-dominated and flat, it can explain the present accelerate expansion of the universe. This is the first study of this class of models using high redshift GRBs. We have performed a $\\chi$-square statistical analysis of the GRBs calibrated with the Cardassian model, and also combined them with both the current Cosmic Microwave Background and Baryonic Acoustic Oscillation data. Our results show consistency between the current observational data and the model predictions. In particular, the best-fit parameters obtained from the $\\chi^2$-analysis are in agreement with those obtained from the Concordance Cosmology ($\\Lambda$-CDM). We determine the redshift at which the universe would start to follow the Cardassian expansion, i. e., \\zc, and both the redshift at which the universe had started to accelerate, i. e., \\zac, and the age-redshift relation $H_0t_0$. Our results also show that the universe, from the point of view of GRBs, had undergo a transition to acceleration at a redshift $z \\approx 0.2-0.7$, which agrees with the SNIa results. Hence, after confronting the Cardassian scenario with the GRBs HD and proving its consistency with it, we conclude that GRBs should indeed be considered a complementary tool to several other astronomical observations for studies of high accuracy in cosmology.

Herman J. Mosquera Cuesta; Habib Dumet M.; Cristina Furlanetto

2007-08-10T23:59:59.000Z

383

Testing a DBI model for the unification of dark matter and dark energy with Gamma-Ray Bursts  

E-Print Network (OSTI)

We study the range of consistency of a model based on a nonlinear scalar field Dirac-Born-Infeld action for the unification of dark matter and dark energy using Gamma-Ray Bursts at high-redshifts. We use the sample of 59 high-redshift GRBs reported by Wei (2010), calibrated at low redshifts with the Union 2 sample of SNe Ia, thus avoiding the circularity problem. In this analysis, we also include the CMB7-year data and the baryonic acoustic peak BAO. Besides, it is calculated the parameter of the equation of state $w$, the deceleration parameter $q_0$ and the redshift of the transition to the decelerate-accelerated phase $z_t$.

Ariadna Montiel; Nora Bretón

2012-02-14T23:59:59.000Z

384

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

385

Models for the circumstellar medium of long gamma-ray burst progenitor candidates.  

E-Print Network (OSTI)

??Long gamma-ray bursts are highly energetic events that are thought to occur when certain massive stars, that end their lives as Wolf-Rayet stars, collapse at… (more)

Marle, A.J. van

2006-01-01T23:59:59.000Z

386

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

387

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

388

An Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical  

Open Energy Info (EERE)

Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical Assessments Of The Volcanic And Plutonic Associations Of Central Anatolia (Turkey) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: An Attempt To Use Aerial Gamma-Ray Spectrometry Results In Petrochemical Assessments Of The Volcanic And Plutonic Associations Of Central Anatolia (Turkey) Details Activities (0) Areas (0) Regions (0) Abstract: Volcanic and magmatic rocks of Central Anatolia 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 additional tool for the petrochemical classification of the volcanic and magmatics rocks and their environments. The survey data on

389

New gamma-ray observatory begins operations at Sierra Negra volcano in the  

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

New gamma-ray observatory begins operations New gamma-ray observatory begins operations New gamma-ray observatory begins operations at Sierra Negra volcano in the state of Puebla, Mexico The High-Altitude Water Cherenkov Gamma Ray Observatory has begun formal operations at its site in Mexico. August 21, 2013 The HAWC Observatory taken in August 2013 from the summit of Sierra Negra. The image has been digitally altered to show HAWC as it will appear when construction is complete in 2014. The 111 Cherenkov detectors currently installed (100 Cherenkov detectors in operation) are colored white and located in the upper right quadrant of the array. The HAWC Observatory taken in August 2013 from the summit of Sierra Negra. The image has been digitally altered to show HAWC as it will appear when construction is complete in 2014. The 111 Cherenkov detectors currently

390

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

E-Print Network (OSTI)

??Milagro is a water-Cherenkov detector that observes the extended air showers produced by cosmic gamma rays of energies E>100GeV. The effective area of Milagro peaks… (more)

Vasileiou, Vlasios

2008-01-01T23:59:59.000Z

391

High-Power Laser Pulse Recirculation for Inverse Compton Scattering-Produced Gamma-Rays  

Science Conference Proceedings (OSTI)

Inverse Compton scattering of high-power laser pulses on relativistic electron bunches represents an attractive method for high-brightness, quasi-monoenergetic {gamma}-ray production. The efficiency of {gamma}-ray generation via inverse Compton scattering is severely constrained by the small Thomson scattering cross section. Furthermore, repetition rates of high-energy short-pulse lasers are poorly matched with those available from electron accelerators, resulting in low repetition rates for generated {gamma}-rays. Laser recirculation has been proposed as a method to address those limitations, but has been limited to only small pulse energies and peak powers. Here we propose and experimentally demonstrate an alternative method for laser pulse recirculation that is uniquely capable of recirculating short pulses with energies exceeding 1 J. Inverse Compton scattering of recirculated Joule-level laser pulses has a potential to produce unprecedented peak and average {gamma}-ray brightness in the next generation of sources.

Jovanovic, I; Shverdin, M; Gibson, D; Brown, C

2007-04-17T23:59:59.000Z

392

A Single Continuous Function as a Model for Fast Rise Exponential Decay Gamma-Ray Bursts.  

E-Print Network (OSTI)

??A quantitative analysis was performed on a sample of Fast-Rise Exponential-Decay gamma-ray bursts using a continuous fitting function. The data were obtained from the Large… (more)

Logue, Daniel B

2006-01-01T23:59:59.000Z

393

GAMMA-RAY BURSTS: NEW PARAMETERS FOR MEASURING ENERGY-DEPENDENT SPECTRAL LAGS.  

E-Print Network (OSTI)

??A new method for measuring the hardness-intensity correlation (HIC) present in gamma-ray bursts (GRB) is developed. This method is used to measure the HIC for… (more)

Durst, Jeff

2009-01-01T23:59:59.000Z

394

Collapsar accretion and the gamma-ray burst X-ray light curve.  

E-Print Network (OSTI)

??We present axisymmetric hydrodynamical simulations of the long-term accretion of a rotating gamma-ray burst progenitor star, a "collapsar," onto the central compact object, which we… (more)

Lindner, Christopher Carl

2010-01-01T23:59:59.000Z

395

How Gravitational-wave Observations Can Shape the Gamma-ray Burst Paradigm  

E-Print Network (OSTI)

By reaching through shrouding blastwaves, efficiently discovering off-axis events, and probing the central engine at work, gravitational wave (GW) observations will soon revolutionize the study of gamma-ray bursts. Already, analyses of GW data targeting gamma-ray bursts have helped constrain the central engines of selected events. Advanced GW detectors with significantly improved sensitivities are under construction. After outlining the GW emission mechanisms from gamma-ray burst progenitors (binary coalescences, stellar core collapses, magnetars, and others) that may be detectable with advanced detectors, we review how GWs will improve our understanding of gamma-ray burst central engines, their astrophysical formation channels, and the prospects and methods for different search strategies. We place special emphasis on multimessenger searches. To achieve the most scientific benefit, GW, electromagnetic, and neutrino observations should be combined to provide greater discriminating power and science reach.

Imre Bartos; Patrick Brady; Szabolcs Marka

2012-12-11T23:59:59.000Z

396

A Search for Short Duration Very High Energy Emission from Gamma-Ray Bursts.  

E-Print Network (OSTI)

??Milagro is a water-Cherenkov detector capable of observing air showers produced by gamma rays with primary energies of approximately 100 GeV and higher. The wide… (more)

Noyes, David Carl

2005-01-01T23:59:59.000Z

397

Studies of intrinsic properties of gamma ray bursts detected by the HETE-II satellite.  

E-Print Network (OSTI)

??Analysis of HETE-II data is discussed with the aim of understanding the intrinsic properties of gamma-ray bursts (GRBs). A technique is developed that allows the… (more)

Csatorday, Peter, 1973-

2007-01-01T23:59:59.000Z

398

Detecting High-Energy Emission from Gamma-Ray Bursts with EGRET and GLAST.  

E-Print Network (OSTI)

??The research described in this dissertation explores the detection of high-energy emission from gamma-ray bursts (GRBs) with EGRET and GLAST. Data from the EGRET experiment… (more)

Wren, David Nathan

2005-01-01T23:59:59.000Z

399

Studies of intrinsic properties of gamma ray bursts detected by the HETE-II satellite  

E-Print Network (OSTI)

Analysis of HETE-II data is discussed with the aim of understanding the intrinsic properties of gamma-ray bursts (GRBs). A technique is developed that allows the simultaneous estimation of source and background counts ...

Csatorday, Peter, 1973-

2007-01-01T23:59:59.000Z

400

Determining the jet opening-angle of gamma-ray bursts  

E-Print Network (OSTI)

There is growing scientific agreement that at least some cosmic gamma-ray bursts (GRBs) coincide with the deaths of rapidly rotating massive stars - dubbed "hyper-novae." In 1987, a supernova (SN 1987A) was detected in the ...

McEvoy, Erica Lynn, 1981-

2004-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


401

EXPLORING SHORT GAMMA-RAY BURSTS AS GRAVITATIONAL-WAVE STANDARD SIRENS  

E-Print Network (OSTI)

Recent observations support the hypothesis that a large fraction of "short-hard" gamma-ray bursts (SHBs) are associated with the inspiral and merger of compact binaries. Since gravitational-wave (GW) measurements of ...

Hughes, Scott A

402

Hybrid Electron-Positron-Ion Shear Flows and Applications to Gamma-Ray Bursts  

E-Print Network (OSTI)

We present Particle-in-Cell simulation results of relativistic shear boundary layers for hybrid electron-positron-ion plasmas and discuss their potential applications to gamma-ray bursts.

Liang, Edison; Smith, Ian

2013-01-01T23:59:59.000Z

403

Very-High-Energy Gamma Rays from a Distant Quasar: How Transparent Is the Universe?  

E-Print Network (OSTI)

The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Since high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.

MAGIC Collaboration; J. Albert

2008-07-17T23:59:59.000Z

404

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

405

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

406

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

407

Time-Integrated Gamma-Ray Burst Synchrotron Spectra from Blast Wave/Cloud Interactions  

E-Print Network (OSTI)

We show that the spectral shape of the low energy tails found for the time-integrated spectra of gamma-ray bursts, even in the absence of strong synchrotron cooling, can be significantly softer than the $\

James Chiang

1998-10-15T23:59:59.000Z

408

Time-Integrated $\\gamma$-Ray Burst Synchrotron Spectra from Blast Wave/Cloud Interactions  

E-Print Network (OSTI)

We show that the spectral shape of the low energy tails found for the time-integrated spectra of gamma-ray bursts, even in the absence of strong synchrotron cooling, can be significantly softer than the $\

Chiang, J

1998-01-01T23:59:59.000Z

409

Semiconductor Radiation Detectors with Frisch Collars and Collimators for Gamma Ray Spectroscopy and Imaging  

SciTech Connect

To study CdZnTe as a high energy resolution gamma ray detector with a novel new design, and to build a detector array from the new detector design

Douglas McGregor; Alireza Kargar; Mark Harrison; Adam Brooks; Walter McNei; Rans Lowell; Adam Graebner

2006-12-04T23:59:59.000Z

410

BATSE Observations of Gamma-Ray Burst Spectra. II. Peak Energy Evolution in Bright, Long Bursts -  

E-Print Network (OSTI)

We investigate spectral evolution in 37 bright, long gamma-ray bursts observed with the BATSE Spectroscopy Detectors. High resolution spectra are characterized by the energy of the peak of \

L. A. Ford; D. L. Band; J. L. Matteson; M. S. Briggs; G. N. Pendleton; R. D. Preece; W. S. Paciesas; B. J. Teegarden; D. M. Palmer; B. E. Schaefer; T. L. Cline; G. J. Fishman; C. Kouveliotou; C. A. Meegan; R. B. Wilson; J. P. Lestrade

1994-07-27T23:59:59.000Z

411

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

412

The 5 March 1979 soft gamma-ray repeater: a fresh outlook  

E-Print Network (OSTI)

An attempt is made to explain the 8-second periodicity of the 5th March 1979 soft gamma-ray repeater as a consequence of the elastic wave precession in the rigid crust of the rotating neutron star.

G. V. Vlasov

1998-07-21T23:59:59.000Z

413

The BeppoSAX revolution in Gamma-Ray Burst science  

E-Print Network (OSTI)

We review the BeppoSAX discoveries and studies in the field of Gamma-Ray Bursts, which allowed a huge step forward in the understanding of these still mysterious and highly interesting astrophysical sources.

L. Amati

2004-05-17T23:59:59.000Z

414

A leptonic-hadronic model for the afterglow of gamma-ray burst 090510  

E-Print Network (OSTI)

We model multiwavelength afterglow data from the short Gamma-Ray Burst (GRB) 090510 using a combined leptonic-hadronic model of synchrotron radiation from an adiabatic blast wave. High energy, >100 MeV, emission in our model is dominated by proton-synchrotron radiation, while electron-synchrotron radiation dominates in the X ray and ultraviolet wavelengths. The collimation-corrected GRB energy, depending on the jet-break time, in this model could be as low as 3e51 erg but two orders of magnitude larger than the gamma-ray energy. We also calculated the opacities for electron-positron pair production by gamma rays and found that TeV gamma rays from proton-synchrotron radiation can escape the blast wave at early time, and their detection can provide evidence of a hadronic emission component dominating at high energies.

Soebur Razzaque

2010-04-20T23:59:59.000Z

415

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

E-Print Network (OSTI)

the University of California. Search for muon neutrinos fromSearch for muon neutrinos from Gamma-Ray Bursts with theWe present the results of searches for high-energy muon

Abbasi, R.

2010-01-01T23:59:59.000Z

416

Black hole neutron star coalescence as a source of gamma-ray bursts  

E-Print Network (OSTI)

We present the results of hydrodynamic (SPH) simulations showing the coalescence of a black hole with a neutron star to be a promising theoretical source of short duration gamma-ray bursts. The favorable features of the process include rapid onset, millisecond variability, a duration much longer than the dynamical timescale, and a range of outcomes sufficient to allow variety in the properties of individual gamma-ray bursts. Interestingly, the process of coalescence differs rather markedly from past predictions.

W. H. Lee; W. Kluzniak

1997-11-14T23:59:59.000Z

417

The Starburst Contribution to the Extra-Galactic Gamma-Ray Background  

E-Print Network (OSTI)

Cosmic ray protons interacting with gas at the mean density of the interstellar medium in starburst galaxies lose energy rapidly via inelastic collisions with ambient nuclei. The resulting pions produce secondary electrons and positrons, high-energy neutrinos, and gamma-ray photons. We estimate the cumulative gamma-ray emission from starburst galaxies. We find a total integrated background above 100 MeV of F_gamma ~ 10^{-6} GeV/cm^2/s/sr and a corresponding specific intensity at GeV energies of nuI_nu ~ 10^{-7} GeV/cm^2/s/sr. Starbursts may thus account for a significant fraction of the extra-galactic $\\gamma$-ray background. We show that the FIR-radio correlation provides a strong constraint on the gamma-ray emission from starburst galaxies because pions decay into both gamma-rays and radio-emitting electron/positron pairs. We identify several nearby systems where the potential for observing gamma-ray emission is the most favorable (M82, NGC 253, and IC 342), predict their fluxes, and predict a linear FIR-gamma-ray correlation for the densest starbursts. If established, the FIR-gamma-ray correlation would provide strong evidence for the ``calorimeter'' theory of the FIR-radio correlation and would imply that cosmic rays in starburst galaxies interact with gas at approximately the mean density of the interstellar medium (ISM), thereby providing an important constraint on the physics of the ISM in starbursts.

Todd A. Thompson; Eliot Quataert; Eli Waxman

2006-06-27T23:59:59.000Z

418

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

419

Constraints on dark matter annihilations from diffuse gamma-ray emission in the Galaxy  

E-Print Network (OSTI)

Recent advances in gamma-ray cosmic ray, infrared and radio astronomy have allowed us to develop a significantly better understanding of the galactic medium properties in the last few years. In this work using the DRAGON code, that numerically solves the CR propagation equation and calculating gamma-ray emissivities in a 2-dimensional grid enclosing the Galaxy, we study in a self consistent manner models for the galactic diffuse gamma-ray emission. Our models are cross-checked to both the available CR and gamma-ray data. We address the extend to which dark matter annihilations in the Galaxy can contribute to the diffuse gamma-ray flux towards different directions on the sky. Moreover we discuss the impact that astrophysical uncertainties of non DM nature, have on the derived gamma-ray limits. Such uncertainties are related to the diffusion properties on the Galaxy, the interstellar gas and the interstellar radiation field energy densities. Light ~10 GeV dark matter annihilating dominantly to hadrons is more strongly constrained by gamma-ray observations towards the inner parts of the Galaxy and influenced the most by assumptions of the gas distribution; while TeV scale DM annihilating dominantly to leptons has its tightest constraints from observations towards the galactic center avoiding the galactic disk plane, with the main astrophysical uncertainty being the radiation field energy density. In addition, we present a method of deriving constraints on the dark matter distribution profile from the diffuse gamma-ray spectra. These results critically depend on the assumed mass of the dark matter particles and the type of its end annihilation products.

Maryam Tavakoli; Ilias Cholis; Carmelo Evoli; Piero Ullio

2013-08-19T23:59:59.000Z

420

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

Science Conference Proceedings (OSTI)

Between 2000 November and 2006 May, one or more spacecraft of the interplanetary network (IPN) detected 226 cosmic gamma-ray bursts that were also detected by the French Gamma-Ray Telescope experiment on board the High Energy Transient Experiment 2 spacecraft. During this period, the IPN consisted of up to nine spacecraft, and using triangulation, the localizations of 157 bursts were obtained. We present the IPN localization data on these events.

Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Atteia, J.-L.; Barraud, C.; Pelangeon, A. [IRAP, Universite de Toulouse, CNRS, 14, avenue Edouard Belin, F-31400 Toulouse (France); Boeer, M. [Observatoire de Haute-Provence, 04870 Saint Michel l'Observatoire (France); Vanderspek, R.; Ricker, G. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States); Mazets, E.; Golenetskii, S.; Frederiks, D. D.; Pal'shin, V. D.; Aptekar, R. L. [Ioffe Physico-Technical Institute of the Russian Academy of Sciences, St. Petersburg, 194021 (Russian Federation); Smith, D. M. [Physics Department and Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States); Wigger, C.; Hajdas, W. [Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Rau, A.; Von Kienlin, A. [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, Postfach 1312, Garching 85748 (Germany); Mitrofanov, I. G.; Golovin, D. V.; Kozyrev, A. S., E-mail: khurley@ssl.berkeley.edu [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); and others

2011-12-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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

Hard x-ray or gamma ray laser by a dense electron beam  

SciTech Connect

A dense electron beam propagating through a laser undulator can radiate a coherent x-ray or gamma ray. This lasing scheme is studied with the Landau damping theory. The analysis suggests that, with currently available physical parameters, coherent gamma rays of up to 50 keV can be generated. The electron quantum diffraction suppresses the free electron laser action, which limits the maximum radiation.

Son, S. [18 Caleb Lane, Princeton, New Jersey 08540 (United States); Joon Moon, Sung [8 Benjamin Rush Ln., Princeton, New Jersey 08540 (United States)

2012-06-15T23:59:59.000Z

422

Ultrahigh Energy Cosmic Rays from Gamma Ray Bursts: Implications of the Recent Observational Results by Milagro  

E-Print Network (OSTI)

It has been speculated earlier that Gamma Ray Bursts are sources of ultrahigh energy cosmic rays. Recently, the search for high energy photons from Gamma Ray Bursts by Milagro group has put limits on the isotropic luminosity of these transient sources in very high energy photons. The implications of the results obtained by Milagro to our understanding of the ultrahigh energy cosmic ray spectrum from these sources have been discussed in the present work.

Nayantara Gupta

2004-06-03T23:59:59.000Z

423

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

424

How Sample Completeness Affects Gamma-Ray Burst Classification  

E-Print Network (OSTI)

Unsupervised pattern recognition algorithms support the existence of three gamma-ray burst classes; Class I (long, large fluence bursts of intermediate spectral hardness), Class II (short, small fluence, hard bursts), and Class III (soft bursts of intermediate durations and fluences). The algorithms surprisingly assign larger membership to Class III than to either of the other two classes. A known systematic bias has been previously used to explain the existence of Class III in terms of Class I; this bias allows the fluences and durations of some bursts to be underestimated (Hakkila et al., ApJ 538, 165, 2000). We show that this bias primarily affects only the longest bursts and cannot explain the bulk of the Class III properties. We resolve the question of Class III existence by demonstrating how samples obtained using standard trigger mechanisms fail to preserve the duration characteristics of small peak flux bursts. Sample incompleteness is thus primarily responsible for the existence of Class III. In order to avoid this incompleteness, we show how a new dual timescale peak flux can be defined in terms of peak flux and fluence. The dual timescale peak flux preserves the duration distribution of faint bursts and correlates better with spectral hardness – 2 – (and presumably redshift) than either peak flux or fluence. The techniques presented here are generic and have applicability to the studies of other transient events. The results also indicate that pattern recognition algorithms are sensitive to sample completeness; this can influence the study of large astronomical databases such as those found in a Virtual Observatory.

Jon Hakkila; Timothy W. Giblin; Richard J. Roiger; David J. Haglin; William S. Paciesas; Charles A. Meegan

2002-01-01T23:59:59.000Z

425

COMPACT BINARY PROGENITORS OF SHORT GAMMA-RAY BURSTS  

SciTech Connect

In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger of such compact binaries is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors that yield SGRBs. By assuming a constant efficiency in converting torus mass into jet energy, {epsilon}{sub jet} = 10%, we find that most of the tori have masses smaller than 0.01 M{sub Sun }, favoring 'high-mass' binary NSs mergers, i.e., binaries with total masses {approx}> 1.5 the maximum mass of an isolated NS. This has important consequences for the gravitational wave signals that may be detected in association with SGRBs, since 'high-mass' systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of {approx}0.9 or higher.

Giacomazzo, Bruno [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, CO 80309 (United States); Perna, Rosalba [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States); Rezzolla, Luciano [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Potsdam D-14476 (Germany); Troja, Eleonora [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Lazzati, Davide [Department of Physics, NC State University, 2401 Stinson Drive, Raleigh, NC 27695-8202 (United States)

2013-01-10T23:59:59.000Z

426

TOWARD TIGHT GAMMA-RAY BURST LUMINOSITY RELATIONS  

Science Conference Proceedings (OSTI)

The large scatters of luminosity relations of gamma-ray bursts (GRBs) have been one of the most important reasons preventing the extensive application of GRBs in cosmology. Many efforts have been made to seek tight luminosity relations. With the latest sample of 116 GRBs with measured redshift and spectral parameters, we investigate 6 two-dimensional (2D) correlations and 14 derived three-dimensional (3D) correlations of GRBs to explore the possibility of decreasing the intrinsic scatters of the luminosity relations of GRBs. We find the 3D correlation of E{sub peak}-{tau}{sub RT}-L to be evidently tighter (at the 2{sigma} confidence level) than its corresponding 2D correlations, i.e., the E{sub peak}-L and {tau}{sub RT}-L correlations. In addition, the coefficients before the logarithms of E{sub peak} and {tau}{sub RT} in the E{sub peak}-{tau}{sub RT}-L correlation are almost exact opposites of each other. Inputting this situation as a prior reduces the relation to L{proportional_to}(E'{sub peak}/{tau}{sub RT}'){sup 0.842{+-}0.064}, where E'{sub peak} and {tau}'{sub RT} denote the peak energy and minimum rise time in the GRB rest frame. We discuss how our findings can be interpreted/understood in the framework of the definition of the luminosity (energy released in units of time). Our argument about the connection between the luminosity relations of GRBs and the definition of the luminosity provides a clear direction for exploring tighter luminosity relations of GRBs in the future.

Qi Shi; Lu Tan, E-mail: qishi11@gmail.com, E-mail: t.lu@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2012-04-20T23:59:59.000Z

427

CANGAROO-III SEARCH FOR TeV GAMMA RAYS FROM TWO CLUSTERS OF GALAXIES  

SciTech Connect

Because accretion and merger shocks in clusters of galaxies may accelerate particles to high energies, clusters are candidate sites for the origin of ultra-high-energy (UHE) cosmic rays. A prediction was presented for gamma-ray emission from a cluster of galaxies at a detectable level with the current generation of imaging atmospheric Cherenkov telescopes. The gamma-ray emission was produced via inverse Compton upscattering of cosmic microwave background photons by electron-positron pairs generated by collisions of UHE cosmic rays in the cluster. We observed two clusters of galaxies, Abell 3667 and Abell 4038, searching for very high energy gamma-ray emission with the CANGAROO-III atmospheric Cherenkov telescope system in 2006. The analysis showed no significant excess around these clusters, yielding upper limits on the gamma-ray emission. From a comparison of the upper limit for the northwest radio relic region of Abell 3667 with a model prediction, we derive a lower limit for the magnetic field of the region of approx0.1 muG. This shows the potential of gamma-ray observations in studies of the cluster environment. We also discuss the flux upper limit from cluster center regions using a model of gamma-ray emission from neutral pions produced in hadronic collisions of cosmic-ray protons with the intracluster medium. The derived upper limit of the cosmic-ray energy density within this framework is an order of magnitude higher than that of our Galaxy.

Kiuchi, R.; Mori, M.; Enomoto, R.; Kifune, T. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Bicknell, G. V. [Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia); Clay, R. W. [School of Chemistry and Physics, University of Adelaide, SA 5005 (Australia); Edwards, P. G. [CSIRO Australia Telescope National Facility, Narrabri, NSW 2390 (Australia); Gunji, S.; Inoue, K. [Department of Physics, Yamagata University, Yamagata City, Yamagata 990-8560 (Japan); Hara, S.; Itoh, C. [Ibaraki Prefectural University of Health Sciences, Ami, Ibaraki 300-0394 (Japan); Hara, T. [Faculty of Management Information, Yamanashi Gakuin University, Kofu, Yamanashi 400-8575 (Japan); Hattori, T.; Kawachi, A. [Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292 (Japan); Hayashi, S.; Kajino, F. [Department of Physics, Konan University, Kobe, Hyogo 658-8501 (Japan); Higashi, Y.; Kabuki, S. [Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Hirai, Y. [Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Katagiri, H. [Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

2009-10-10T23:59:59.000Z

428

Gamma-Rays from Grazing Incidence Cosmic Rays in the Earth’s Atmosphere  

E-Print Network (OSTI)

Interactions of grazing incidence, ultra high energy cosmic rays with the earth’s atmosphere may provide a new method of studying energetic cosmic rays with gamma-ray satellites. It is found that these cosmic ray interactions may produce gamma-rays on millisecond time scales which may be detectable by satellites. An extremely low gamma-ray background for transient gamma-ray events and a large area of interaction, the earth’s surface, make the scheme plausible. The effective cross section of detection of interactions for cosmic rays above 1020 eV is found to be more than two orders of magnitude higher than earth based detection techniques. This method may eventually offer an efficient way of probing this region of the cosmic ray energy spectrum where events are scarce. In this paper, a conceptual model is presented for the production of short bursts of gamma-rays based on these grazing incidence encounters with the earth’s atmosphere. Subject headings: atmospheric effects- cosmic rays- Earth- gamma-rays: bursts

Andrew Ulmer

1994-01-01T23:59:59.000Z

429

1 Gamma-Ray Burst Spectra and Time Histories From 2 to 400 keV  

E-Print Network (OSTI)

The Gamma-Ray burst detector on Ginga consisted of a proportional counter to observe the x-rays and a scintillation counter to observe the gamma-rays. It was ideally suited to study the x-rays associated with gammaray bursts (GRBs). Ginga detected ? 120 GRBs and 22 of them had sufficient statistics to determine spectra from 2 to 400 keV. Although the Ginga and BATSE trigger criteria were very similar, the distribution of spectral parameters was different. Ginga observed bend energies in the spectra down to 2 keV and had a larger fraction of bursts with low energy power law indexes greater than zero. The average ratio of energy in the x-ray band (2 to 10 keV) compared to the gamma-ray band (50 to 300 keV) was 24%. Some events had more energy in the x-ray band than in the gamma-ray band. One Ginga event had a period of time preceding the gamma rays that was effectively pure x-ray emission. This x-ray “preactivity ” might be due to the penchant for the GRB time structure to be broader at lower energy rather than a different physical process. The x-rays tend to rise and fall slower than the gamma rays but they both tend to peak at about the same time. This argues against models involving the injection of relativistic electrons that cool by synchrotron radiation. 1.

E. E. Fenimore

1998-01-01T23:59:59.000Z

430

Neutron-induced gamma-ray spectroscopy: simulations for chemical mapping of planetary surfaces  

DOE Green Energy (OSTI)

Cosmic rays interact with the surface of a planetary body and produce a cascade of secondary particles, such as neutrons. Neutron-induced scattering and capture reactions play an important role in the production of discrete gamma-ray lines that can be measured by a gamma-ray spectrometer on board of an orbiting spacecraft. These data can be used to determine the concentration of many elements in the surface of a planetary body, which provides clues to its bulk composition and in turn to its origin and evolution. To investigate the gamma rays made by neutron interactions, thin targets were irradiated with neutrons having energies from 14 MeV to 0.025 eV. By means of foil activation technique the ratio of epithermal to thermal neutrons was determined to be similar to that in the Moon. Gamma rays emitted by the targets and the surrounding material were detected by a high-resolution germanium detector in the energy range of 0.1 to 8 MeV. Most of the gamma-ray lines that are expected to be used for planetary gamma-ray spectroscopy were found in the recorded spectra and the principal lines in these spectra are presented. 58 refs., 7 figs., 9 tabs.

Brueckner, J.; Waenke, H.; Reedy, R.C.

1986-01-01T23:59:59.000Z

431

Angular two-point correlation functions for cosmological gamma-ray burst model  

E-Print Network (OSTI)

We compute the angular two-point correlation functions of the gamma-ray bursts at cosmological distances. Since the gamma-ray burst emission mechanism is not yet established, we simply assume that the gamma-ray burst sources are associated with high-redshift galaxies in some way. Then on the basis of several simple models for the evolution of galaxy spatial correlations, we calculate the amplitude of angular two-point correlation functions on scales appropriate for the Compton Gamma Ray Observatory data. we find that in most cases the predicted correlations are difficult to detect with the current data rate and the angular resolution, but models in which the bursts preferentially occur at relatively low redshift ($z \\simlt 0.5$) predict correlation amplitudes on $\\theta \\sim 5^\\circ$ which will be marginally detectable with the Gamma Ray Observatory data in several years. If future observations detect a signal of angular correlations, it will imply useful information on the correlation of galaxies at high redshifts provided that the gamma-ray bursts are cosmological.

Shiho Kobayashi; Shin Sasaki; Yasushi Suto

1994-09-16T23:59:59.000Z

432

Gamma-ray spectra and doses from the Little Boy replica  

SciTech Connect

Most radiation safety guidelines in the nuclear industry are based on the data concerning the survivors of the nuclear explosions at Hiroshima and Nagasaki. Crucial to determining these guidelines is the radiation from the explosions. We have measured gamma-ray pulse-height distributions from an accurate replica of the Little Boy device used at Hiroshima, operated at low power levels near critical. The device was placed outdoors on a stand 4 m from the ground to minimize environmental effects. The power levels were based on a monitor detector calibrated very carefully in independent experiments. High-resolution pulse-height distributions were acquired with a germanium detector to identify the lines and to obtain line intensities. The 7631 to 7645 keV doublet from neutron capture in the heavy steel case was dominant. Low-resolution pulse-height distributions were acquired with bismuth-germanate detectors. We calculated flux spectra from these distributions using accurately measured detector response functions and efficiency curves. We then calculated dose-rate spectra from the flux spectra using a flux-to-dose-rate conversion procedure. The integral of each dose-rate spectrum gave an integral dose rate. The integral doses at 2 m ranged from 0.46 to 1.03 mrem per 10/sup 13/ fissions. The output of the Little Boy replica can be calculated with Monte Carlo codes. Comparison of our experimental spectra, line intensities, and integral doses can be used to verify these calculations at low power levels and give increased confidence to the calculated values from the explosion at Hiroshima. These calculations then can be used to establish better radiation safety guidelines. 7 references, 7 figures, 2 tables.

Moss, C.E.; Lucas, M.C.; Tisinger, E.W.; Hamm, M.E.

1984-01-01T23:59:59.000Z

433

ILLUMINATING THE DARKEST GAMMA-RAY BURSTS WITH RADIO OBSERVATIONS  

Science Conference Proceedings (OSTI)

We present X-ray, optical, near-infrared (IR), and radio observations of gamma-ray bursts (GRBs) 110709B and 111215A, as well as optical and near-IR observations of their host galaxies. The combination of X-ray detections and deep optical/near-IR limits establish both bursts as ''dark''. Sub-arcsecond positions enabled by radio detections lead to robust host galaxy associations, with optical detections that indicate z {approx}bursts are dark due to substantial rest-frame extinction. Using the radio and X-ray data for each burst we find that GRB 110709B requires A{sub V}{sup host}{approx}>5.3 mag and GRB 111215A requires A{sub V}{sup host}{approx}>8.5 mag (assuming z = 2). These are among the largest extinction values inferred for dark bursts to date. The two bursts also exhibit large neutral hydrogen column densities of N{sub H,{sub int}} {approx}> 10{sup 22} cm{sup -2} (z = 2) as inferred from their X-ray spectra, in agreement with the trend for dark GRBs. Moreover, the inferred values are in agreement with the Galactic A{sub V} -N{sub H} relation, unlike the bulk of the GRB population. Finally, we find that for both bursts the afterglow emission is best explained by a collimated outflow with a total beaming-corrected energy of E{sub {gamma}} + E{sub K} Almost-Equal-To (7-9) Multiplication-Sign 10{sup 51} erg (z = 2) expanding into a wind medium with a high density, M Almost-Equal-To (6-20) Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1} (n Almost-Equal-To 100-350 cm{sup -3} at Almost-Equal-To 10{sup 17} cm). While the energy release is typical of long GRBs, the inferred density may be indicative of larger mass-loss rates for GRB progenitors in dusty (and hence metal rich) environments. This study establishes the critical role of radio observations in demonstrating the origin and properties of dark GRBs. Observations with the JVLA and ALMA will provide a sample with sub-arcsecond positions and robust host associations that will help to shed light on obscured star formation and the role of metallicity in GRB progenitors.

Zauderer, B. A.; Berger, E.; Margutti, R.; Fong, W.; Laskar, T.; Chornock, R.; Soderberg, A. M. [Department of Astronomy, Harvard University, Cambridge, MA 02138 (United States); Levan, A. J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Olivares E, F.; Greiner, J. [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Perley, D. A.; Horesh, A.; Carpenter, J. [Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91225 (United States); Updike, A. C. [Department of Chemistry and Physics, Roger Williams University, Bristol, RI 02809 (United States); Tanvir, N. R. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Menten, K. M. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Nakar, E. [Department of Astrophysics, Sackler School of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv (Israel); Chandra, P. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Ganeshkhind, Pune 411007 (India); Castro-Tirado, A. J. [Instituto de Astrofisica de Andalucia (IAA-CSIC), P.O. Box 03004, E-18080 Granada (Spain); Bremer, M. [Institut de Radioastronomie Millimetrique, 300 rue de la Piscine, F-38406 Saint Martin d'Heres (France); and others

2013-04-20T23:59:59.000Z

434

Mon. Not. R. Astron. Soc. 374, 14731478 (2007) doi:10.1111/j.1365-2966.2006.11249.x The Swift gamma-ray burst GRB 050422  

E-Print Network (OSTI)

gamma-ray burst GRB 050422 A. P. Beardmore,1 K. L. Page,1 P. T. O'Brien,1 J. P. Osborne,1 S. Kobayashi,2 of GRB 050422, a Swift-discovered gamma-ray burst. The prompt gamma-ray emission had a T90 duration of 59 afterglow model. Key words: gamma-rays: bursts. 1 INTRODUCTION Gamma-ray bursts (GRBs) are highly energetic

Zhang, Bing

435

Lithium-6 and Gamma Rays: Complementary Constraints on Cosmic-Ray History  

E-Print Network (OSTI)

The rare isotope 6Li is made only by cosmic rays, dominantly in alpha+alpha fusion reactions with ISM helium. Consequently, this nuclide provides a unique diagnostic of the history of cosmic rays in our Galaxy. The same hadronic cosmic-ray interactions also produce high-energy gamma rays (mostly via neutral pion production). Thus, hadronic gamma-rays and 6Li are intimately linked. Specifically, 6Li directly encodes the local cosmic-ray fluence over cosmic time, while extragalactic hadronic gamma rays encode an average cosmic-ray fluence over lines of sight out to the horizon. We examine this link and show how 6Li and gamma-rays can be used together to place important model-independent limits on the cosmic-ray history of our Galaxy and the universe. We first constrain gamma-ray production from ordinary Galactic cosmic rays, using the local 6Li abundance. We find that the solar 6Li abundance demands an accompanying extragalactic pionic gamma-ray intensity which exceeds that of the entire observed EGRB by a factor of 2-6. Possible explanations for this discrepancy are discussed. We then constrain Li production using recent determinations of extragalactic gamma-ray background (EGRB). We note that cosmic rays created during cosmic structure formation would lead to pre-Galactic Li production, which would act as a "contaminant" to the primordial 7Li content of metal-poor halo stars. We find the uncertainties in the observed EGRB are so large that we cannot exclude a pre-Galactic Li which is comparable to primordial 7Li. Our limits and their more model-dependent extensions will improve significantly with additional observations of 6Li in halo stars, and with improved measurements of the EGRB spectrum by GLAST. (Abriged abstract)

Brian D. Fields; Tijana Prodanovic

2004-07-15T23:59:59.000Z

436

GRB 090727 AND GAMMA-RAY BURSTS WITH EARLY-TIME OPTICAL EMISSION  

SciTech Connect

We present a multi-wavelength analysis of Swift gamma-ray burst GRB 090727, for which optical emission was detected during the prompt gamma-ray emission by the 2 m autonomous robotic Liverpool Telescope and subsequently monitored for a further two days with the Liverpool and Faulkes Telescopes. Within the context of the standard fireball model, we rule out a reverse shock origin for the early-time optical emission in GRB 090727 and instead conclude that the early-time optical flash likely corresponds to emission from an internal dissipation process. Putting GRB 090727 into a broader observational and theoretical context, we build a sample of 36 gamma-ray bursts (GRBs) with contemporaneous early-time optical and gamma-ray detections. From these GRBs, we extract a sub-sample of 18 GRBs, which show optical peaks during prompt gamma-ray emission, and perform detailed temporal and spectral analysis in gamma-ray, X-ray, and optical bands. We find that in most cases early-time optical emission shows sharp and steep behavior, and notice a rich diversity of spectral properties. Using a simple internal shock dissipation model, we show that the emission during prompt GRB phase can occur at very different frequencies via synchrotron radiation. Based on the results obtained from observations and simulation, we conclude that the standard external shock interpretation for early-time optical emission is disfavored in most cases due to sharp peaks ({Delta}t/t < 1) and steep rise/decay indices, and that internal dissipation can explain the properties of GRBs with optical peaks during gamma-ray emission.

Kopac, D.; Gomboc, A.; Japelj, J. [Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana (Slovenia); Kobayashi, S.; Mundell, C. G.; Bersier, D.; Cano, Z.; Smith, R. J.; Steele, I. A.; Virgili, F. J. [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead, CH41 1LD (United Kingdom); Guidorzi, C. [Physics Departments, University of Ferrara, via Saragat 1, I-44122, Ferrara (Italy); Melandri, A., E-mail: drejc.kopac@fmf.uni-lj.si [INAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy)

2013-07-20T23:59:59.000Z

437

Development of a New Cs137 Gamma-ray Calibration Facility  

Science Conference Proceedings (OSTI)

... in which radiation detection instruments can be ... It is divided into two areas (control and irradiation ... to place radiation measuring instrumentation at a ...

2013-03-13T23:59:59.000Z

438

Study of Gamma-Ray Bursts of energy E 10 GeV with the ARGO-YBJ detector  

E-Print Network (OSTI)

, and it is now detecting about one confirmed gamma-ray or soft gamma repeater burst every 2.5 days. It has detected almost 900 events so far. Keywords: gamma-ray bursts, experiments PACS: 98.70.Rz INTRODUCTION We of the Suzaku Hard X-Ray Detector Wideband All-Sky Monitor (HXD WAM) has been designed to act as a gamma-ray

Morselli, Aldo

439

Gamma-Ray Bursts as a Cosmic Window for Galaxy Evolution  

E-Print Network (OSTI)

Present knowledge indicates that gamma-ray bursts are linked with massive stars. They will become invaluable probes of the early universe and galaxy formation. In the future, it will be possible to use gamma-ray bursts for two purposes: 1) to probe the history of massive star formation in the Universe by the rate of occurence of gamma-ray bursts, and 2) for the study of galaxy evolution at all lookback times by determining the nature of the galaxy hosts. Because gamma-rays are not attenuated by intervening dust and gas, the selection of the cosmic sites of massive star formation by this method is less affected by the biases associated with optical-uv surveys (e.g. UV-dropout techniques). Infrared and sub-millimeter follow up studies of the hosts of gamma-ray bursts may: 1) reveal a putative population of reddened ($R-K \\geq 4$) galaxies at high redshifts, and 2) detect very massive stars (population III) formed at $z \\geq$ 5.

I. F. Mirabel; D. B. Sanders; E. Le Floc'h

2000-04-03T23:59:59.000Z

440

A Remarkable Angular Distribution of the Intermediate Subclass of Gamma-Ray Bursts  

E-Print Network (OSTI)

In the article a test is developed, which allows to test the null-hypothesis of the intrinsic randomness in the angular distribution of gamma-ray bursts collected at the Current BATSE Catalog. The method is a modified version of the well-known counts-in-cells test, and fully eliminates the non-uniform sky-exposure function of BATSE instrument. Applying this method to the case of all gamma-ray bursts no intrinsic non-randomness is found. The test also did not find intrinsic non-randomnesses for the short and long gamma-ray bursts, respectively. On the other hand, using the method to the new intermediate subclass of gamma-ray bursts, the null-hypothesis of the intrinsic randomness for 181 intermediate gamma-ray bursts is rejected on the 96.4% confidence level. Taking 92 dimmer bursts from this subclass itself, we obtain the surprising result: This "dim" subclass of the intermediate subclass has an intrinsic non-randomness on the 99.3% confidence level. On the other hand, the 89 "bright" bursts show no intrinsic non-randomness.

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

2000-03-20T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray calibration blocks" 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.


441

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

442

Evidence for Post-Quiescent, High-Energy Emission from Gamma-Ray Burst 990104  

E-Print Network (OSTI)

It is well known that high-energy emission (MeV-GeV) has been observed in a number of gamma-ray bursts, and temporally-extended emission from lowerenergy gamma rays through radio wavelengths is well established. An important observed characteristic of some bursts at low energy is quiescence: an initial emission followed by a quiet period before a second (post-quiescent) emission. Evidence for significant high-energy, post-quiescent emission has been lacking. Here we present evidence for high-energy emission, coincident with lower energy emission, from the post-quiescent emission episode of the very bright and long burst, GRB 990104. We show light curves and spectra that confirm emission above 50 MeV, approximately 152 seconds after the BATSE trigger and initial emission episode. Between the initial emission episode and the main peak, seen at both low and high energy, there was a quiescent period of ?100 s during which the burst was relatively quiet. This burst was found as part of an ongoing search for high-energy emission in gamma-ray bursts using the EGRET fixed interval (32 s) accumulation spectra, which provide sensitivity to later, high-energy emission that is otherwise missed by the standard EGRET BATSE-triggered burst spectra. Subject headings: gamma rays: bursts—gamma rays: observations – 2 –

D. N. Wren; D. L. Bertsch; S. Ritz

2002-01-01T23:59:59.000Z

443

Gamma-Ray Bursts Observed with the Spectrometer SPI Onboard INTEGRAL  

E-Print Network (OSTI)

The spectrometer SPI is one of the main detectors of ESA's INTEGRAL mission. The instrument offers two interesting and valuable capabilities for the detection of the prompt emission of Gamma-ray bursts. Within a field of view of 16 degrees, SPI is able to localize Gamma-ray bursts with an accuracy of 10 arcmin. The large anticoincidence shield, ACS, consisting of 512 kg of BGO crystals, detects Gamma-ray bursts quasi omnidirectionally above ~70 keV. Burst alerts from SPI/ACS are distributed to the interested community via the INTEGRAL Burst Alert System. The ACS data have been implemented into the 3rd Interplanetary Network and have proven valuable for the localization of bursts using the triangulation method. During the first 8 months of the mission approximately one Gamma-ray burst per month was localized within the field of fiew of SPI and 145 Gamma-ray burst candidates were detected by the ACS from which 40 % have been confirmed by other instruments.

A. von Kienlin; A. Rau; V. Beckmann; S. Deluit

2004-07-07T23:59:59.000Z

444

A Search for TeV Gamma-Ray Burst Emission with the Milagro Observatory  

E-Print Network (OSTI)

The Milagro telescope monitors the northern sky for 100 GeV - 100 TeV transient emission through continuous very high energy wide-field observations. The large effective area and low energy threshold of Milagro allow it to detect very high energy gamma-ray burst emission with much higher sensitivity than previous instruments, and a fluence sensitivity at TeV energies comparable to dedicated gamma-ray burst satellites at keV-MeV energies. Observation of gamma-ray burst emission at TeV energies could place important constraints on gamma-ray burst progenitor and emission models. This study details the development of a weighted analysis technique; the implementation of this technique to perform a real time search for TeV transients of 40 seconds to 3 hours duration in the Milagro data; and the results from more than one year of observation. Between May 2nd, 2001, and May 22nd, 2002, no TeV transients of 40 seconds to 3 hours duration were observed. Upper limits on both observed and emitted high energy gamma-ray burst emission are presented.

Miguel F. Morales

2003-08-06T23:59:59.000Z

445

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

446

Signatures of photon and axion-like particle mixing in the gamma-ray burst jet  

E-Print Network (OSTI)

Photons couple to Axion-Like Particles (ALPs) or more generally to any pseudo Nambu-Goldstone boson in the presence of an external electromagnetic field. Mixing between photons and ALPs in the strong magnetic field of a Gamma-Ray Burst (GRB) jet during the prompt emission phase can leave observable imprints on the gamma-ray polarization and spectrum. Mixing in the intergalactic medium is not expected to modify these signatures for ALP mass > 10^(-14) eV and/or for gamma ray emission. We also show that when the magnetic field orientation in the propagation region is perpendicular to the field orientation in the production region, the observed synchrotron spectrum becomes steeper than the theoretical prediction and as detected in a sizable fraction of GRB sample. Detection of the correlated polarization and spectral signatures from these steep-spectrum GRBs by gamma-ray polarimeters can be a very powerful probe to discover ALPs. Measurement of gamma-ray polarization from GRBs in general, with high statistics, can also be useful to search for ALPs.

Olga Mena; Soebur Razzaque; F. Villaescusa-Navarro

2011-01-10T23:59:59.000Z

447

RELATIVISTIC SHOCK BREAKOUTS-A VARIETY OF GAMMA-RAY FLARES: FROM LOW-LUMINOSITY GAMMA-RAY BURSTS TO TYPE Ia SUPERNOVAE  

SciTech Connect

The light from a shock breakout of stellar explosions, which carries a wealth of information, strongly depends on the shock velocity at the time of the breakout. The emission from Newtonian breakouts, typical in regular core-collapse supernovae (SNe), has been explored extensively. However, a large variety of explosions result in mildly or ultrarelativistic breakouts, where the observed signature is unknown. Here we calculate the luminosity and spectrum produced by relativistic breakouts. In order to do so, we improve the analytic description of relativistic radiation-mediated shocks and follow the system from the breakout itself, through the planar phase and into the spherical phase. We limit our calculation to cases where the post-breakout acceleration of the gas ends during the planar phase (i.e., the final gas Lorentz factor {approx}< 30). We find that spherical relativistic breakouts produce a flash of gamma rays with energy, E{sub bo}, temperature, T{sub bo}, and duration, t{sup obs} b{sub o}, that provide the breakout radius ( Almost-Equal-To 5 R{sub Sun }(t{sup obs}{sub bo}/10 s)(T{sub bo}/50 keV){sup 2}) and the Lorentz factor ( Almost-Equal-To T{sub bo}/50 keV). They also always satisfy a relativistic breakout relation (t{sup obs}{sub bo}/20 s) {approx} (E{sub bo}/10{sup 46} erg){sup 1/2}(T{sub bo}/50 keV){sup -2.68}. The breakout flare is typically followed, on longer timescales, by X-rays that carry a comparable energy. We apply our model to a variety of explosions, including Type Ia and .Ia SNe, accretion-induced collapse, energetic SNe, and gamma-ray bursts (GRBs). We find that all these events produce detectable gamma-ray signals, some of which may have already been seen. Some particular examples are: (1) relativistic shock breakouts provide a natural explanation to the energy, temperature, and timescales of low-luminosity GRBs. Indeed, all observed low-luminosity GRBs satisfy the relativistic breakout relation. (2) Nearby broad-line Type Ib/c (like SN 2002ap) may produce a detectable {gamma}-ray signal. (3) Galactic Type Ia SNe may produce detectable {gamma}-ray flares. We conclude that relativistic shock breakouts provide a generic process for the production of gamma-ray flares.

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

2012-03-10T23:59:59.000Z

448

CANGAROO-III OBSERVATION OF TeV GAMMA RAYS FROM THE VICINITY OF PSR B1706-44  

Science Conference Proceedings (OSTI)

Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov Telescope has detected extended emission of TeV gamma rays in the vicinity of the pulsar PSR B1706-44. The strength of the signal observed as gamma-ray-like events varies when we apply different ways of emulating background events. The reason for such uncertainties is argued in relevance to gamma rays embedded in the 'OFF-source data', that is, unknown sources and diffuse emission in the Galactic plane, namely, the existence of a complex structure of TeV gamma-ray emission around PSR B1706-44.

Enomoto, R.; Kifune, T. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Kushida, J.; Hattori, T.; Ishioka, H.; Kawachi, A. [Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292 (Japan); Nakamori, T. [Department of Basic Physics, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551 (Japan); Bicknell, G. V. [Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia); Clay, R. W. [School of Chemistry and Physics, University of Adelaide, SA 5005 (Australia); Edwards, P. G. [Narrabri Observatory of the Australia Telescope National Facility, CSIRO, Epping, NSW 2121 (Australia); Gunji, S.; Inoue, K. [Department of Physics, Yamagata University, Yamagata 990-8560 (Japan); Hara, S. [Ibaraki Prefectural University of Health Sciences, Ami, Ibaraki 300-0394 (Japan); Hara, T. [Faculty of Management Information, Yamanashi Gakuin University, Kofu, Yamanashi 400-8575 (Japan); Hayashi, S.; Kajino, F. [Department of Physics, Konan University, Kobe, Hyogo 658-8501 (Japan); Higashi, Y.; Kabuki, S. [Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Hirai, Y. [Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Katagiri, H. [Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

2009-10-01T23:59:59.000Z

449

Studies on the gamma-ray burst phenomenon and on its use to probe the high redshift universe.  

E-Print Network (OSTI)

??Gamma-ray bursts (GRBs) are an enigmatic phenomenon whose physics and origins are still to be fully understood. Furthermore, thanks to their exceptional brightness they can… (more)

Vergani, Susanna D.

2009-01-01T23:59:59.000Z

450

Rapid response monitoring of transient radio emission associated with gamma-ray bursts and circinus X-1.  

E-Print Network (OSTI)

??This PhD project was aimed at carrying out comprehensive observational studies of radio sources associated with two types of transients: a) Gamma- Ray Bursts (GRBs)… (more)

Moin, Aquib

2011-01-01T23:59:59.000Z

451

The Collimation Signatures of Gamma-Ray Bursts: Jet Properties and Energetic Inferred from X-ray Afterglow Observations.  

E-Print Network (OSTI)

??Our understanding of gamma-ray bursts (GRBs) and their afterglows has progressed dramatically over the last few years thanks to the Swift mission and progress in… (more)

Racusin, Judith

2009-01-01T23:59:59.000Z

452

Response to 'A comment on "Signatures of fissile materials: High-energy gamma rays following fission," by Zeev B. Alfassi'  

E-Print Network (OSTI)

high-energy ? rays following fission" by Zeev B. Alfassi ,radionuclides that are not fission products, but which emittemporal variation of the fission product gamma rays should

2004-01-01T23:59:59.000Z

453

Prompt TeV Emission from Cosmic Rays Accelerated by Gamma Ray Bursts Interacting with Surrounding Stellar Wind  

E-Print Network (OSTI)

Protons accelerated in the internal shocks of a long duration gamma ray burst can escape the fireball as cosmic rays by converting to neutrons. Hadronic interactions of these neutrons inside a stellar wind bubble created by the progenitor star will produce TeV gamma rays via neutral meson decay and synchrotron radiation by charged pion-decay electrons in the wind magnetic field. Such gamma rays should be observable from nearby gamma ray bursts by currently running and upcoming ground-based detectors.

Soebur Razzaque; Olga Mena; Charles D. Dermer

2008-10-07T23:59:59.000Z

454

Strict Limit on CPT Violation from Polarization of Gamma-Ray Bursts  

E-Print Network (OSTI)

We report the strictest observational verification of CPT invariance in the photon sector, as a result of gamma-ray polarization measurement of distant gamma-ray bursts (GRBs), which are brightest stellar-size explosions in the universe. We detected the gamma-ray polarization of three GRBs with high significance, and the source distances may be constrained by a well-known luminosity indicator for GRBs. For the Lorentz- and CPT-violating dispersion relation E_{\\pm}^2=p^2 \\pm 2\\xi p^3/M_{Pl}, where \\pm denotes different circular polarization states of the photon, the parameter \\xi is constrained as |\\xi|

Kenji Toma; Shinji Mukohyama; Daisuke Yonetoku; Toshio Murakami; Shuichi Gunji; Tatehiro Mihara; Yoshiyuki Morihara; Tomonori Sakashita; Takuya Takahashi; Yudai Wakashima; Hajime Yonemochi; Noriyuki Toukairin

2012-08-27T23:59:59.000Z

455

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

456

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

457

Prospects for Type Ia Supernova explosion mechanism identification with gamma rays  

E-Print Network (OSTI)

The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. There is a wide agreement that high amounts of of radioactive nuclei are produced during these events and they are expected to be strong gamma-ray emitters. In the past, several authors have investigated the use of this gamma-ray emission as a diagnostic tool. In this paper we have done a complete study of the gamma-ray spectra associated with all the different scenarios currently proposed. This includes detonation, delayed detonation, deflagration and the off-center detonation. We have performed accurate simulations for this complete set of models in order to determine the most promising spectral features that could be used to discriminate among the different models. Our study is not limited to qualitative arguments. Instead, we have quantified the differences among the spectra and established distance limits for their detection. The calculations have been performed considering the best current response estim...

Gómez-Gomar, J; Jean, P; Gomez-Gomar, Jordi; Isern, Jordi; Jean, Pierre

1997-01-01T23:59:59.000Z

458

Superradiant control of gamma-ray propagation by vibrating nuclear arrays  

E-Print Network (OSTI)

The collective nature of light interactions with atomic and nuclear ensembles yields the fascinating phenomena of superradiance and radiation trapping. We study the interaction of gamma rays with a coherently vibrating periodic array of two-level nuclei. Such nuclear motion can be generated, e.g., in ionic crystals illuminated by a strong driving optical laser field. We find that deflection of the incident gamma beam into the Bragg angle can be switched on and off by nuclear vibrations on a superradiant time scale determined by the collective nuclear frequency, which is of the order of terahertz. Namely, if the incident gamma wave is detuned from the nuclear transition by much larger frequency it passes through the static nuclear array. However, if the nuclei vibrate with the frequency of the gamma ray detuning then parametric resonance can yield energy transfer into the Bragg deflected beam on the superradiant time scale, which can be used for fast control of gamma rays.

Xiwen Zhang; Anatoly A. Svidzinsky

2013-09-30T23:59:59.000Z

459

Real time method and computer system for identifying radioactive materials from HPGe gamma-ray spectroscopy  

DOE Patents (OSTI)

A real-time method and computer system for identifying radioactive materials which collects gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum. A library of nuclear material definitions ("library definitions") is provided, with each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum. The method determines whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of the library definitions, and subsequently uniquely identifies the material type as that nuclide or isotope material associated with the satisfied library definition. The method is iteratively repeated to update the spectrum and identification in real time.

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)

2007-10-23T23:59:59.000Z

460

Exploring simultaneous single and coincident gamma-ray measurements for U/Pu assay in safeguards  

Science Conference Proceedings (OSTI)

Using a broad range of gamma-ray uranium standards and two plutonium samples of known isotopic content, list mode gamma ray information from two Compton suppressed and one planar HPGe detectors were analyzed according to the time information of the signals. Interferences from Cs-137 were introduced. In this study, we extended singles measurements by exploring the potential of simultaneously using both singles and coincidence data for U/Pu assay. The main goals of this exploratory study are: 1) whether one will be able to use coincidence information in addition to the complicated 100-keV unfolding to obtain extra information of uranium and plutonium isotopic ratios, and 2) with higher energy interference gamma-rays from isotopes such as Cs-137, can the coincidence information help to provide the isotopic information. (authors)

Wang, T. F. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Horne, S. M. [Nuclear and Radiation Engineering Program, Mechanical Engineering Dept., Univ. of Texas at Austin, Austin, TX 78712 (United States); Henderson, R. A.; Roberts, K. E.; Vogt, D. K. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)

2011-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "gamma-ray calibration blocks" from the National Library of EnergyBeta (NLEBeta).
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to obtain the most current and comprehensive results.


461

Accurate calculations of the WIMP halo around the Sun and prospects for gamma ray detection  

E-Print Network (OSTI)

Weakly interacting massive particles (WIMPs) can be captured by heavenly objects, like the Sun. Under the process of being captured by the Sun, they will build up a population of WIMPs around it, that will eventually sink to the core of the Sun. It has been argued with simpler estimates before that this halo of WIMPs around the Sun could be a strong enough gamma ray source to be a detectable signature for WIMP dark matter. We here revisit the problem using detailed Monte Carlo simulations and detailed composition and structure information about the Sun to estimate the size of the gamma ray flux. Compared to earlier estimates, we find that the gamma ray flux from WIMP annihilations in the Sun halo would be negligible and no current or planned detectors would even be able to detect this flux.

Sivertsson, Sofia

2009-01-01T23:59:59.000Z

462

Accurate calculations of the WIMP halo around the Sun and prospects for its gamma ray detection  

E-Print Network (OSTI)

Weakly interacting massive particles (WIMPs) can be captured by heavenly objects, like the Sun. Under the process of being captured by the Sun, they will build up a population of WIMPs around it, which will eventually sink to the core. It has been suggested that this halo of WIMPs around the Sun could be a gamma ray source, possibly distinct enough to have nice detectable signature for WIMP dark matter. We here revisit this problem using detailed Monte Carlo simulations and detailed composition and structure information about the Sun to estimate the size of the gamma ray flux. Compared to earlier simpler estimates, we find that the gamma ray flux from WIMP annihilations in the Sun halo would be negligible; no current or planned detectors would be able to detect this flux.

Sivertsson, Sofia

2009-01-01T23:59:59.000Z

463

Implications of Neutrino Balls as the Source of Gamma-Ray Bursts  

E-Print Network (OSTI)

(To appear in the Astrophysical Journal) Holdom and Malaney (1994) have suggested a mechanism for gamma-ray bursts which requires that stars be captured by a neutrino ball. Neutrino balls would be, for the most part, denser than main sequence stars, but their density would decrease as their mass increased. We show that small neutrino balls would subject stars to tidal forces sufficient to disrupt them. We thus argue that if neutrino balls existed at the centres of galaxies, only the largest would be able to act as a source of gamma-ray bursts. Such neutrino balls would have a mass of order $10^7\\Msun$. Tidal capture of stars by a neutrino ball would not be important, but dynamical friction against the neutrinos or star-disc interactions could both be important capture mechanisms. We find that a gamma-ray burst would occur in a galaxy containing such a neutrino ball roughly every $10^2\\y$, and the fraction of all galaxies contributing to the gamma-ray burst flux would be $\\sim 10^{-4}$, assuming that this was the mechanism of all gamma-ray bursts. These numbers have implications for neutrino ball models of active galaxies, assuming that all gamma-ray bursts and all AGN come from neutrino balls. Either a small fraction $\\sim 10^{-2}$ of the lifetime of such an object could be spent as an AGN, or that the probability of a neutrino ball becoming an AGN would be $10^{-2}$. It is not possible to rule out the possibility that neutrino balls might exist at the centres of galaxies through direct ground-based observation of stellar kinematics.

D. Syer; Cita

1994-06-10T23:59:59.000Z

464

Revealing Type Ia supernova physics with cosmic rates and nuclear gamma rays  

E-Print Network (OSTI)

Type Ia supernovae (SNIa) remain mysterious despite their central importance in cosmology and their rapidly increasing discovery rate. The progenitors of SNIa can be probed by the delay time between progenitor birth and explosion as SNIa. The explosions and progenitors of SNIa can be probed by MeV nuclear gamma rays emitted in the decays of radioactive nickel and cobalt into iron. We compare the cosmic star formation and SNIa rates, finding that their different redshift evolution requires a large fraction of SNIa to have large delay times. A delay time distribution of the form t^{-1.0 +/- 0.3} provides a good fit, implying 50% of SNIa explode more than ~ 1 Gyr after progenitor birth. The extrapolation of the cosmic SNIa rate to z = 0 agrees with the rate we deduce from catalogs of local SNIa. We investigate prospects for gamma-ray telescopes to exploit the facts that escaping gamma rays directly reveal the power source of SNIa and uniquely provide tomography of the expanding ejecta. We find large improvements relative to earlier studies by Gehrels et al. in 1987 and Timmes & Woosley in 1997 due to larger and more certain SNIa rates and advances in gamma-ray detectors. The proposed Advanced Compton Telescope, with a narrow-line sensitivity ~ 60 times better than that of current satellites, would, on an annual basis, detect up to ~ 100 SNIa (3 sigma) and provide revolutionary model discrimination for SNIa within 20 Mpc, with gamma-ray light curves measured with ~ 10 sigma significance daily for ~ 100 days. Even more modest improvements in detector sensitivity would open a new and invaluable astronomy with frequent SNIa gamma-ray detections.

Shunsaku Horiuchi; John F. Beacom

2010-06-30T23:59:59.000Z

465

Compton Electrons and Electromagnetic Pulse in Supernovae and Gamma-Ray Bursts  

E-Print Network (OSTI)

When gamma-rays emerge from a central source they may undergo Compton scattering in surrounding matter. The resulting Compton-scattered electrons radiate. Coherent radiation by such Compton electrons follows nuclear explosions above the Earth's atmosphere. Particle acceleration in instabilities produced by Compton electron currents may explain the radio emission by SN1998bw. Bounds on coherent radiation are suggested for supernovae and gamma-ray bursts; these bounds are very high, but it is unknown if coherent radiation occurs in these objects.

J. I. Katz

1999-08-19T23:59:59.000Z

466

Conversion of neutron stars to strange stars as the central engine of gamma-ray bursts  

E-Print Network (OSTI)

We study the conversion of a neutron star to a strange star as a possible energy source for gamma-ray bursts. We use different recent models for the equation of state of neutron star matter and strange quark matter. We show that the total amount of energy liberated in the conversion is in the range of (1-4) 10^{53} ergs (one order of magnitude larger than previous estimates) and is in agreement with the energy required to power gamma-ray burst sources at cosmological distances.

Ignazio Bombaci; Bhaskar Datta

2000-01-27T23:59:59.000Z

467

White Paper on the Status and Future of Ground-based Gamma-ray Astronomy  

E-Print Network (OSTI)

In recent years, ground-based gamma-ray observatories have made a number of important astrophysical discoveries which have attracted the attention of the wider scientific community. The Division of Astrophysics of the American Physical Society has requested the preparation of a white paper on the status and future of ground-based gamma-ray astronomy to define the science goals of the future observatory, to determine the performance specifications, and to identify the areas of necessary technology development. In this contribution we give a brief overview of the activities of the current white paper team and invite the international community to contribute to the white paper.

Krawczynski, H; Byrum, K; Dermer, C; Dingus, B; Falcone, A; Kaaret, Philip; Krennrich, F; Pohl, M; Vasilev, V; Williams, D A

2007-01-01T23:59:59.000Z

468

White Paper on the Status and Future of Ground-based Gamma-ray Astronomy  

E-Print Network (OSTI)

In recent years, ground-based gamma-ray observatories have made a number of important astrophysical discoveries which have attracted the attention of the wider scientific community. The Division of Astrophysics of the American Physical Society has requested the preparation of a white paper on the status and future of ground-based gamma-ray astronomy to define the science goals of the future observatory, to determine the performance specifications, and to identify the areas of necessary technology development. In this contribution we give a brief overview of the activities of the current white paper team and invite the international community to contribute to the white paper.

H. Krawczynski; J. Buckley; K. Byrum; C. Dermer; B. Dingus; A. Falcone; P. Kaaret; F. Krennrich; M. Pohl; V. Vassiliev; D. A. Williams; for the White Paper Team

2007-09-05T23:59:59.000Z

469

Lag-luminosity relation in gamma-ray burst X-ray flares  

Science Conference Proceedings (OSTI)

In strict analogy to prompt pulses, X-ray flares observed by Swift-XRT in long Gamma-Ray Bursts define a lag-luminosity relation: L{sub p,iso}{sup 0.3-10} k{sup eV} {infinity}t{sub lag}{sup -0.95{+-}0.23}. The lag-luminosity is proven to be a fundamental law extending {approx}5 decades in time and {approx}5 in energy. This is direct evidence that GRB X-ray flares and prompt gamma-ray pulses are produced by the same mechanism.

Margutti, R.

2010-10-15T23:59:59.000Z

470

Variable Very High Energy Gamma-ray Emission from the Microquasar LS I +61 303  

E-Print Network (OSTI)

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and laboratories for elucidating the physics of relativistic jets. Here we report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I +61 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, suggesting the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or the absorption processes.

MAGIC Collaboration; J. Albert

2006-05-22T23:59:59.000Z

471

SHORT GAMMA-RAY BURSTS AND DARK MATTER SEEDING IN NEUTRON STARS  

SciTech Connect

We present a mechanism based on internal self-annihilation of dark matter accreted from the galactic halo in the inner regions of neutron stars that may trigger full or partial conversion into a quark star. We explain how this effect may induce a gamma-ray burst (GRB) that could be classified as short, according to the usual definition based on time duration of the prompt gamma-ray emission. This mechanism differs in many aspects from the most discussed scenario associating short GRBs with compact object binary mergers. We list possible observational signatures that should help distinguish between these two possible classes of progenitors.

Perez-Garcia, M. Angeles [Department of Fundamental Physics and IUFFyM, University of Salamanca, Plaza de la Merced s/n, E-37008 Salamanca (Spain); Daigne, F.; Silk, J., E-mail: mperezga@usal.es, E-mail: daigne@iap.fr, E-mail: j.silk1@physics.ox.ac.uk [UPMC-CNRS, UMR7095, Institut d'Astrophysique de Paris, F-75014 Paris (France)

2013-05-10T23:59:59.000Z

472

A Method to Search for Local Sources of Short Duration Bursts of Superhigh Energy Gamma Rays  

E-Print Network (OSTI)

A method of a search for local sources of superhigh energy gamma rays is described in the paper.It is shown that the method is more effective then the usually used method extracting excess from total intensity if gamma ray burst durations are short.Using the suggested method,the information detected with the Baksan installation ``Carpet'' during 1992-1996 years was analyzed.An excess of event numbers was found at the confidence level of 6.5$\\sigma$ in the direction to Mrk 501.

E. N. Alexeyev; D. D. Djappuev; A. U. Kudjaev; S. Kh. Ozrokov

2000-10-02T23:59:59.000Z

473

GRB941017: A Case Study of Neutrino Production in Gamma Ray Bursts  

E-Print Network (OSTI)

GRB941017, a gamma-ray burst of exceptional fluence, has recently been shown to have a high-energy component which is not consistent with the standard fireball phenomenology. If this component is the result of photomeson interactions in the burst fireball, it provides new and compelling support for substantial high-energy neutrino fluxes from this and similar sources. In this letter, we consider what impact this new information has on the neutrino spectra of gamma-ray bursts and discuss how this new evidence impacts the prospects for detection of such events in next generation neutrino telescopes.

Jaime Alvarez-Muñiz; Francis Halzen; Dan Hooper

2003-10-15T23:59:59.000Z

474

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

E-Print Network (OSTI)

We outline the scientific motivation behind a search for gravitational waves associated 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 boxes of different shapes and sizes and a search on these error boxes poses a series of challenges for data analysis. We will discuss these challenges and outline the methods to optimise the search over these error boxes.

V. Predoi; for the LIGO Scientific Collaboration; for the Virgo Collaboration; K. Hurley; for IPN

2011-12-07T23:59:59.000Z

475

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

476

The Gamma Ray Burst section of the White Paper on the Status and Future of Very High Energy Gamma Ray Astronomy A Brief Preliminary Report  

E-Print Network (OSTI)

This is a short report on the preliminary findings of the gamma ray burst (GRB) working group for the white paper on the status and future of very high energy (VHE; >50 GeV) gamma-ray astronomy. The white paper discusses the status of past and current attempts to observe GRBs at GeV-TeV energies, including a handful of low-significance, possible detections. The white paper concentrates 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 the detection of VHE emission would have strong implications for GRB models, as well as cosmic ray origin. In particular, the extended emission phase (including both afterglow emission and possible flaring) of nearby long GRBs could provide the best possibility for detection. The difficult-to-obtain observations during the prompt phase of nearby long GRBs and short GRBs could also provide particularly str...

Falcone, A D; Baring, M G; Blandford, R; Connaughton, V; Coppi, P; Dermer, C; Dingus, B; Fryer, C; Gehrels, N; Granot, J; Horan, D; Katz, J I; Kühn, K; Mészáros, P; Norris, J; Parkinson, P Saz; Peér, A; Ramirez-Ruiz, E; Razzaque, S; Wang, X; Zhang, B

2008-01-01T23:59:59.000Z

477

The Gamma Ray Burst section of the White Paper on the Status and Future of Very High Energy Gamma Ray Astronomy: A Brief Preliminary Report  

E-Print Network (OSTI)

This is a short report on the preliminary findings of the gamma ray burst (GRB) working group for the white paper on the status and future of very high energy (VHE; >50 GeV) gamma-ray astronomy. The white paper discusses the status of past and current attempts to observe GRBs at GeV-TeV energies, including a handful of low-significance, possible detections. The white paper concentrates 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 the detection of VHE emission would have strong implications for GRB models, as well as cosmic ray origin. In particular, the extended emission phase (including both afterglow emission and possible flaring) of nearby long GRBs could provide the best possibility for detection. The difficult-to-obtain observations during the prompt phase of nearby long GRBs and short GR