Mizuta, Akira 2010 二维模拟喷流及热辐射

主要内容:
该喷流的热辐射还可以解释GeV光子的延迟。

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Title:		Thermal Radiation from GRB Jets
Authors:		Mizuta, Akira; Nagataki, Shigehiro; Aoi, Junichi
Publication:		eprint arXiv:1006.2440
Publication Date:		06/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		13 pages, 4 figures, submitted to ApJL
Bibliographic Code:		2010arXiv1006.2440M

Abstract

In this study, the light curves and spectrum of the photospheric thermal radiation from ultrarelativistic gamma-ray burst (GRB) jets are calculated using 2D relativistic hydrodynamic simulations of jets from a collapsar. As the jet advances, the density around its head of the jet decreases, and its Lorentz factor reaches as high as 200 at the photosphere and 400 inside the photosphere. For an on-axis observer, the photosphere appears concave shaped due to the low density and high beaming factor of the jet. The light curve for the first phases is flared for all viewing angles. For an on-axis observer, luminosity varies because of the abrupt change in the position of the photosphere due to the internal structure of the jet. Comparing our results with those of GRB090902B, we conclude that GRB090902B had a more collimated jet with a higher temperature and/or beaming factor than that of our simulation. The spectrum for an on-axis observer is harder than that for an off-axis observer. There is a time lag of a few seconds for high energy bands in the light curve, which may be the reason for the delayed onset seen in GRB080916C.

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