Detection of a spectral break in the extra hard component of GRB 090926A

Preprint

12 January 2011

preprint
Published by arXiv in arXiv

https://doi.org/10.48550/arXiv.1101.2082

Abstract

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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All Related Versions

Version 1, 2011-01-11, ArXiv
Version 2, 2011-01-12, ArXiv
Published version: The Astrophysical Journal, 729 (2), 114.

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