Takami 2007 通过X射线早期快下降阶段来推测喷流结构

主要内容:
细致研究不同结构的喷流的tail emission导致的光变曲线的下降指数。方法是蒙特卡罗模拟。

精彩摘抄:


文章信息:
Probing the Structure of Gamma-Ray Burst Jets with Steep Decay Phase of their Early X-ray Afterglows

Authors: Kentaro Takami (1), Ryo Yamazaki (1), Takanori Sakamoto (2), Goro Sato (2) ((1) Hiroshima Univ., (2) NASA/GSFC)

(Submitted on 9 Apr 2007 (v1), last revised 13 Apr 2007 (this version, v2))

Abstract: We show that the jet structure of gamma-ray bursts (GRBs) can be investigated with the tail emission of the prompt GRB. The tail emission which we consider is identified as a steep-decay component of the early X-ray afterglow observed by the X-ray Telescope onboard Swift. Using a Monte Carlo method, we derive, for the first time, the distribution of the decay index of the GRB tail emission for various jet models. The new definitions of the zero of time and the time interval of a fitting region are proposed. These definitions for fitting the light curve lead us an unique definition of the decay index, which is useful to investigate the structure of the GRB jet. We find that if the GRB jet has a core-envelope structure, the predicted distribution of the decay index of the tail has a wide scatter and has multiple peaks, which cannot be seen for the case of the uniform and the Gaussian jet. Therefore, the decay index distribution tells us the information on the jet structure. Especially, if we observe events whose decay index is less than about 2, both the uniform and the Gaussian jet models will be disfavored according to our simulation study.

Comments:

21 pages, 10 figures, ApJ in press, the paper with full resolution images is this http URL

Subjects:

Astrophysics (astro-ph)

Cite as:

arXiv:0704.1055v2 [astro-ph]