van Eerten, H. J. 2010 数值模拟喷流的拐折

主要内容:
喷流拐折本来应该是全波段的，但他们说射电可能会晚很多。
模拟结果显示比一般的估计也就相差一倍多。

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Title:		Jet simulations and Gamma-ray burst afterglow jet breaks
Authors:		van Eerten, H. J.; Meliani, Z.; Wijers, R. A. M. J.; Keppens, R.
Publication:		eprint arXiv:1005.3966
Publication Date:		05/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		MNRAS submitted. 9 pages, 12 figures
Bibliographic Code:		2010arXiv1005.3966V

Abstract

The conventional derivation of the gamma-ray burst afterglow jet break time uses only the blast wave fluid Lorentz factor and therefore leads to an achromatic break. We show that in general gamma-ray burst afterglow jet breaks are chromatic across the self-absorption break. Depending on circumstances, the radio jet break may be postponed significantly. Using high-accuracy adaptive mesh fluid simulations in one dimension, coupled to a detailed synchrotron radiation code, we demonstrate that this is true even for the standard fireball model and hard-edged jets. We confirm these effects with a simulation in two dimensions. The frequency dependence of the jet break is a result of the angle dependence of the emission, the changing optical depth in the self-absorbed regime and the shape of the synchrotron spectrum in general. In the optically thin case the conventional analysis systematically overestimates the jet break time, leading to inferred opening angles that are underestimated by a factor 1.32 and explosion energies that are underestimated by a factor 1.73, for explosions in a homogeneous environment.

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