Barniol 2008 早期快降的绝热膨胀解释

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· arXiv e-print (arXiv:0806.1226)

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Title:		Adiabatic expansion, early x-ray data and the central engine in GRBs
Authors:		Barniol Duran, R.; Kumar, P.
Publication:		eprint arXiv:0806.1226
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, 2 figures, submitted for publication on MNRAS
Bibliographic Code:		2008arXiv0806.1226B

Abstract

The Swift satellite early x-ray data shows a very steep decay in most of the Gamma-Ray Bursts light curves. This decay is either produced by the rapidly declining continuation of the central engine activity or by some left-over radiation starting right after the central engine shuts off. The latter scenario consists of the emission from an "ember" that cools via adiabatic expansion and, if the jet angle is larger than the inverse of the source Lorentz factor, the large angle emission. In this work, we calculate the temporal and spectral properties of the emission from such a cooling ember, providing a new treatment for the micro-physics of the adiabatic expansion. We compare the theoretical expectations of the adiabatic expansion (and the large angle emission) with the current observations of the early x-ray data and find that only about 20% of our sample of 107 bursts is potentially consistent with this model. This leads us to believe that, for most bursts, the central engine does not turn off completely during the steep decay of the x-ray light curve; therefore, this phase is produced by the continued rapidly declining activity of the central engine.

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