Sakamoto 2007 Swift暴快下降阶段的数据统计

主要内容:
不是像其他人将BAT延伸到XRT再作光变曲线，而是反过来。说下降用指数衰减比用幂律衰减更好拟合。得到的结论说快下降阶段不支持曲率效应的解释，给出可能是早期外激波的。（主要还是给出了很多处理过的数据）

精彩摘抄:
横坐标是时间幂律指数alpha，纵坐标是光子谱指数gamma，如果是曲率效应，则alpha＝gamma＋1，应该是虚线所表示的。但这些暴没有一个经过虚线。

对X射线的幂律拟合，如果只看后面的红线，选择不同的t0，和时间指数alpha都能很好地拟合！

文章信息:

arXiv:0707.2170 [ps, pdf, other]

Title: Evidence of Exponential Decay Emission in the Swift Gamma-ray Bursts

Authors: T. Sakamoto, J. E. Hill, R. Yamazaki, L. Angelini, H. A. Krimm, G. Sato, S. Swindell, K. Takami, J. P. Osborne

Comments: 33 pages, 34 figures; accepted for publication in ApJ

Subjects: Astrophysics (astro-ph)

We present a systematic study of the steep decay emission from gamma-ray bursts (GRBs) observed by the Swift X-Ray Telescope (XRT). In contrast to the analysis described in recent literature, we produce composite Burst Alert Telescope (BAT) and XRT light curves by extrapolating the XRT data (2-10 keV) into the BAT energy range (15-25 keV) rather than extrapolating the BAT data into the XRT energy band (0.3-10 keV). Based on the fits to the composite light curves, we have confirmed the existence of an exponential decay component which smoothly connects the BAT prompt data to the XRT steep decay for several GRBs. We also find that the XRT steep decay for some of the bursts can be well fit by a combination of a power-law with an exponential decay model. We discuss this exponential component within the frame work of both the internal and the external shock model.