Ghirlanda, G. 2009 GRB 090510的晚期GeV辐射可能是来自余辉

主要内容:
说LAT的余辉的高能. 不过看到这么光滑的光变, 应该确实是的. 但是减速时标只有0.3秒!

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Title:		The onset of the GeV afterglow of GRB 090510
Authors:		Ghirlanda, G.; Ghisellini, G.; Nava, L.
Publication:		eprint arXiv:0909.0016
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		4 pages, 3 figures, submitted to ApJ Letters
Bibliographic Code:		2009arXiv0909.0016G

Abstract

We study the emission of the short/hard GRB 090510 at energies > 0.1 GeV as observed by the Large Area Telescope (LAT) onboard the Fermi satellite. The GeV flux rises in time as t^2 and decays as t^-1.5 up to 200 s. The peak of the high energy flux is delayed by 0.2 s with respect to the main ~MeV pulse detected by the Fermi Gamma Burst Monitor (GBM). Its energy spectrum is consistent with F(E)=E^-1. The time behavior and the spectrum of the high energy LAT flux are strong evidences of an afterglow origin. We then interpret it as synchrotron radiation produced by the forward shock of a fireball having a bulk Lorentz factor Gamma ~ 2000. The afterglow peak time is independent of energy in the 0.1-30 GeV range and coincides with the arrival time of the highest energy photon (~ 30 GeV). Since the flux detected by the GBM and the LAT have different origins, the delay between these two components is not entirely due to possible violation of the Lorentz invariance. It is the LAT component by itself that allows to set a stringent lower limit on the quantum-gravity mass of 4.7 times the Planck mass.

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