Hydrodynamics of relativistic blast waves in a density-jump medium and their emission signature

被引:72
作者
Dai, ZG [1 ]
Lu, T [1 ]
机构
[1] Nanjing Univ, Dept Astron, Nanjing 210093, Peoples R China
基金
中国国家自然科学基金;
关键词
gamma rays : bursts; relativity; shock waves;
D O I
10.1086/339418
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We analyze in detail the hydrodynamics and afterglow emission of an ultrarelativistic blast wave when it expands in a density-jump medium. Such a medium is likely to appear in the vicinity of gamma-ray bursts (GRBs) associated with massive stars. The interaction of the blast wave with this medium is described through a reverse shock and a forward shock. We show that the reverse shock is initially relativistic if the factor of a density jump (alpha) is much larger than 21 and Newtonian if 1 < alpha<< 21. We also calculate light curves of the afterglow emission during the interaction if the reverse shock is relativistic and find that the optical flux density initially decays abruptly, then rises rapidly, and finally fades based on a power law, which could be followed by an abrupt decay when the reverse shock has just crossed the originally swept-up matter. Therefore, one property of an afterglow occurring in a large density-jump medium is an abrupt drop followed by a bump in the light curve and thus provides a probe of circumburst environments. In addition, this property may not only account for the optical afterglows of GRB 970508 and GRB 000301C but may also explain the X-ray afterglow of GRB 981226.
引用
收藏
页码:L87 / L90
页数:4
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