Shen 2008 dust模型不能解释X射线余辉的平降阶段

主要内容:


精彩摘抄:


文章信息:

· arXiv e-print (arXiv:0806.3541)

· References in the Article

· Also-Read Articles (Reads History)

·

· Translate This Page

Title:		The Dust Scattering Model Can Not Explain The Shallow X-ray Decay in GRB Afterglows
Authors:		Shen, Rong-Feng; Willingale, Richard; Kumar, Pawan; O'Brien, Paul T.; Evans, Phil A.
Publication:		eprint arXiv:0806.3541
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		9 pages, 6 figures, submitted to MNRAS
Bibliographic Code:		2008arXiv0806.3541S

Abstract

A dust scattering model was recently proposed to explain the shallow X-ray decay (plateau) observed prevalently in Gamma-Ray Burst (GRB) early afterglows. In this model the plateau is the scattered prompt X-ray emission by the dust located close (about 10 to a few hundred pc) to the GRB site. In this paper we carefully investigate the model and find that the scattered emission undergoes strong spectral softening with time, due to the model's essential ingredient that harder X-ray photons have smaller scattering angle thus arrive earlier, while softer photons suffer larger angle scattering and arrive later. The model predicts a significant change, i.e., $\Delta \beta \sim 2 - 3$, in the X-ray spectral index from the beginning of the plateau toward the end of the plateau, while the observed data shows close to zero softening during the plateau and the plateau-to-normal transition phase. The scattering model predicts a big difference between the harder X-ray light curve and the softer X-ray light curve, i.e., the plateau in harder X-rays ends much earlier than in softer X-rays. This feature is not seen in the data. The large scattering optical depths of the dust required by the model imply strong extinction in optical, $A_V \gtrsim $ 10, which contradicts current findings of $A_V= 0.1 - 0.7$ from optical and X-ray afterglow observations. We conclude that the dust scattering model can not explain the X-ray plateaus.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)