Urata 2007 有一些暴的“正常”阶段也不能用标准余辉模型解释

主要内容:
他们选择“正常”下降阶段的光学和X射线的时间指数（f_nu\propto t^{-alpha}），按照标准模型，（alpha_O-alpha_X）应该在－1／4到5／4之间，但有些却在－1／4以下，说明标准余辉模型不能解释。

不过在文中作者并没有考虑同步自吸收的情形，(即nu_O .lt. nu_a .lt. nu_x, nu_o .lt. nu_m .lt. nu_x的也没有考虑。还是不够全面的。而且如果光学小于同步自吸收的话，光学的指数是负的，x射线是正的，一定可以小于-1/4


精彩摘抄:
所考虑的几种情形
alpha_O and alpha_X


几个暴的数据

文章信息:

arXiv:0707.2826 [ps, pdf, other]

Title: Testing the External Shock Model of Gamma-Ray Bursts using the Late-Time Simultaneous Optical and X-ray Afterglows

Authors: Yuji Urata, Ryo Yamazaki, Takanori Sakamoto, Kuiyun Huang, Weikang Zheng, Goro Sato, Tsutomu Aoki, Jinsong Deng, Kunihito Ioka, WingHuen Ip, Koji S. Kawabata, YiHsi Lee, Xin Liping, Hiroyuki Mito, Takashi Miyata, Yoshikazu Nakada, Takashi Ohsugi, Yulei Qiu, Takao Soyano, Kenichi Tarusawa, Makoto Tashiro, Makoto Uemura, Jianyan Wei, Takuya Yamashita

Comments: 12 page, 2 figures, 2 tables. Submitted to ApJL

Subjects: Astrophysics (astro-ph)

We study the ``normal'' decay phase of the X-ray afterglows of gamma-ray bursts (GRBs), which follows the shallow decay phase, using the events simultaneously observed in the R-band. The classical external shock model, in which neither the delayed energy injection nor time-dependency of shock micro-physics is considered, shows that the decay indices of the X-ray and R-band light curves, $\alpha_{\rm X}$ and $\alpha_{\rm O}$, obey a certain relation, and that in particular, $\alpha_{\rm O}-\alpha_{\rm X}$ should be larger than -1/4. For our selected 14 samples, we have found that 7 events violate the limit taking into account 1$\sigma$ error, so that a fraction of events are outliers of the classical external shock model at the ``normal'' decay phase.