Where are Swift Gamma-ray bursts beyond the "synchrotron deathline"?

Savchenko, V.
Neronov, A.
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We study time-resolved spectra of the prompt emission of Swift Gamma-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low energy photon indices harder than 2/3 are consistent with Swift data. We perform a systematic search of the episodes of the spectral hardening down to the photon indices below 2/3 in the prompt emission spectra of Swift GRBs. We show that the data of the BAT instrument on board of Swift are consistent with BATSE data, if one takes into account differences between the two instruments. Much lower statistics of the very hard spectra in Swift GRBs is explained by the smaller field of view and narrower energy band of the BAT telescope.
Comment: 11 pages, 20 figures, accepted for publication in MNRAS
Astrophysics - High Energy Astrophysical Phenomena