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Accession Number
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DE2012-1045814
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Title
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Detection of a Spectral Break in the Extra Hard Component of GRB 090926A.
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Publication Date
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Jan 2011
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Media Count
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31p
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Personal Author
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G. Barbiellini J. Ballet K. Asano L. Baldini M. Ackerman M. Ajello M. Axelsson
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Abstract
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We report on the observation of the bright, long gamma-ray burst, GRB 090926A, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on board the Fermi Gamma-ray Space Telescope. GRB 090926A shares several features with other bright LAT bursts. In particular, it clearly shows a short spike in the light curve that is present in all detectors that see the burst, and this in turn suggests that there is a common region of emission across the entire Fermi energy range. In addition, while a separate high-energy power-law component has already been observed in other GRBs, here we report for the first time the detection with good significance of a high-energy spectral break (or cutoff) in this power-law component around 1.4 GeV in the time-integrated spectrum. If the spectral break is caused by opacity to electron-positron pair production within the source, then this observation allows us to compute the bulk Lorentz factor for the outflow, rather than a lower limit.
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Keywords
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Detection
Energy range
Eolectron-positron interactions
Fermi gamma ray space telescope
Gamma ray burst
Monitors
Pair production
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Source Agency
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Technical Information Center Oak Ridge Tennessee
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NTIS Subject Category
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54C - Astrophysics
54D - Cosmic Ray Research
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Corporate Author
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Stanford Research Inst., Menlo Park, CA.
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Document Type
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Technical report
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Title Note
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N/A
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NTIS Issue Number
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1303
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Contract Number
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DE-AC02-76SF00515
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