EGRET observations of bursts at MeV energies

Journal Article · Sat May 16 04:00:00 EDT 1998 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.55340· OSTI ID:21185789

Catelli, J R ^[1]; Dingus, B L ^[2]; Schneid, E J ^[3]

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1. Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)
2. Department of Physics, University of Utah, Salt Lake City, Utah 84112 (United States)
3. Northrop Grumman Co., MS A01-26, Bethpage, New York 11714 (United States)

We present preliminary results from the analysis of 16 bright bursts that have been observed by the EGRET NaI calorimeter, or TASC. Seven bursts have been imaged in the EGRET spark chamber above 30 MeV, but in most cases the TASC data gives the highest energy spectra available for these bursts. The TASC can obtain spectral and rate information for bursts well outside the field of view of the EGRET spark chambers, and is sensitive in the energy range from 1 to 200 MeV. The spectra for these bursts are mostly consistent with a simple power law with spectral index in the range from 1.7 to 3.7, with several of the brighter bursts showing emission past 100 MeV. No high energy cutoff has been observed. These high energy photons offer important clues to the physical processes involved at the origin of burst emission. For bursts at cosmological distances extremely high bulk Lorentz factors are implied by the presence of MeV and GeV photons which have not been attenuated by pair production with the lower energy photons from the source.

• OSTI ID: 21185789
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 428; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
COSMIC GAMMA BURSTS
COSMIC GAMMA SOURCES
COSMIC PHOTONS
COSMIC RAY DETECTION
GAMMA DETECTION
GAMMA SPECTRA
GEV RANGE
MEV RANGE
NAI DETECTORS
PAIR PRODUCTION
PHOTON EMISSION
SHOWER COUNTERS
SPARK CHAMBERS