Global Properties of X-ray Afterglows Observed with Swift/XRT
A comprehensive analysis of the X-ray afterglows of GRBs from the early shallow decay to late jet like decayphases observed with Swift/XRT is presented. We find that no significant spectral evolution is observed from the shallowto normal decay segments in the XRT lightcurves, and the normal decay segment is roughly consistent with external-shockmodels, favoring the idea that the shallow decay segment may be due to long-lasted refreshed shocks, but the observedchromatic breaks in the X-ray and optical bands of some bursts raise concerns for this scenario. GRBs 060413, 060522,060607A, and 070110 are four significant outliers of this scenario in our sample, and they likely have an internal origin,which demands continuous operation of a long-term central engine. In order to explore the late jet-like breaks in the afterglowlight curves we analyze the Swift XRT data for 179 GRBs and the optical afterglow data for 57 pre-and post-Swift GRBs.We find that no textbook version of jet break is found, in which the data fully satisfy jet break criteria. By relaxing one ormore requirements, candidates to various degrees are identified. The break time in the X-ray band is earlier than that in theoptical bands, and among thirteen bursts having both the optical and X-ray light curves, only seven have an achromatic break.Even in these cases only one band data satisfies the closure relations. These are great issues to interpret these candidates as jetbreaks and further inferring GRB energetics.
Gamma-ray bursts Statistical
En-Wei Liang Bin-Bin Zhang Bing Zhang
College of Physical Science & Technology,Guangxi University,Nanning,530004,China Department of Physics & Astrophysics,University of Nevada,Las Vegas
国际会议
2008 NanJing Gamma-Ray Burst Conference(2008年伽马暴国际研讨会)
南京
英文
25-30
2008-06-23（万方平台首次上网日期，不代表论文的发表时间）