Nardini, M. 2009 检查早期余辉中光学和X射线之间是否单一幂律

主要内容:
这需要先把X射线的低能段的谱指数找出来(比较难,因为有吸收). 然后和光学的观测比较, 看是否在这个谱指数的延伸上. 结果发现有些不是单一谱, 暗示光学和X射线可能来自不同的起源. 从而也是二者光变不一致的原因.

分析了好几个暴的谱.

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Title:		Testing a new view of Gamma Ray Burst Afterglows
Authors:		Nardini, M.; Ghisellini, G.; Ghirlanda, G.; Celotti, A.
Publication:		eprint arXiv:0907.4157
Publication Date:		07/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		12 pages, 11 figures, submitted to MNRAS
Bibliographic Code:		2009arXiv0907.4157N

Abstract

The optical and X-ray light-curves of long Gamma Ray Bursts (GRBs) often show a complex evolution and in most cases do not track each other. This behaviour can not be easily explained by the simplest standard afterglow models. A possible interpretation is to consider the observed optical and X-ray light-curves as the sum of two separate components. This scenario requires the presence of a spectral break between these bands. One of the aims of this work is to test whether such a break is present within the observed Swift XRT energy range. We analyse the X-ray afterglow spectra of a sample of 33 long GRBs with known redshift, good optical photometry and published estimate of the host galaxy dust absorption A_V(host). We find that indeed in 7 bright events a broken power-law provides a fit to the data that is better than a single power-law model. For 8 events, instead, the X-ray spectrum is better fitted by a single power-law. We discuss the role of these breaks in connection to the relation between the host hydrogen column density N_H(host) and A_V(host) and check the consistency of the X-ray spectral breaks with the optical bands photometry. We analyse the optical to X-ray spectral energy distributions at different times and find again consistency with two components interpretation.

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