Physical Processes Shaping Gamma-Ray Burst X-Ray Afterglow Light Curves: Theoretical Implications from the Swift X-Ray Telescope Observations
Physical Processes Shaping Gamma-Ray Burst X-Ray Afterglow Light Curves: Theoretical Implications from the Swift X-Ray Telescope Observations
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DOI：
10.1086/500723
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
Bing Zhang;Yizhong Fan;Yizhong Fan;J. Dyks;S. Kobayashi;S. Kobayashi;P. Mészáros;D. Burrows
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文献类型：
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作者：
Bing Zhang;Yizhong Fan;Yizhong Fan;J. Dyks;S. Kobayashi;S. Kobayashi;P. Mészáros;D. Burrows
随着雨燕伽马射线暴探测器的成功发射，其机载X射线望远镜（XRT）收集了丰富的早期X射线余辉数据。一些有趣的功能正在出现，包括一个独特的快速衰减组件之前的传统余辉组件在许多来源，一个浅的衰变组件之前，更“正常”的衰变组件中观察到的一个很好的一部分伽玛暴，和X射线耀斑在近一半的余辉。在本文中，我们系统地分析了塑造早期X射线余辉光曲线性质的可能物理过程，并使用数据来约束各种模型。我们认为，陡峭的衰变分量是一致的瞬发γ射线爆发和/或X射线耀斑的尾部发射。这有力地证明了瞬发辐射和余辉辐射可能是两个不同的成分，支持了伽玛射线暴瞬发辐射的内部起源。在一组伽玛射线暴中观察到的浅衰变段表明，前向激波很可能会持续刷新一段时间。这可能是由一个长寿命的中央发动机，或广泛分布的壳洛伦兹因子，或者可能是减速的坡印廷通量为主的流动。X射线耀斑表明，伽玛射线暴的中心引擎很可能在伽玛射线爆发结束后仍然活跃，但在稍后的时间活动减少。在某些情况下，中央引擎的活动甚至延续到爆发触发后的几天。早期的X射线余辉数据的分析表明，伽玛暴确实是高度相对论性的事件和早期余辉数据的许多爆发，从开始的XRT观测，是一致的余辉发射从ISM环境。
With the successful launch of the Swift Gamma-Ray Burst Explorer, a rich trove of early X-ray afterglow data has been collected by its onboard X-Ray Telescope (XRT). Some interesting features are emerging, including a distinct rapidly decaying component preceding the conventional afterglow component in many sources, a shallow decay component before the more "normal" decay component observed in a good fraction of GRBs, and X-ray flares in nearly half of the afterglows. In this paper we systematically analyze the possible physical processes that shape the properties of the early X-ray afterglow light curves and use the data to constrain various models. We suggest that the steep decay component is consistent with the tail emission of the prompt gamma-ray bursts and/or the X-ray flares. This provides strong evidence that the prompt emission and afterglow emission are likely two distinct components, supporting the internal origin of the GRB prompt emission. The shallow decay segment observed in a group of GRBs suggests that very likely the forward shock keeps being refreshed for some time. This might be caused by either a long-lived central engine, or a wide distribution of the shell Lorentz factors, or else possibly the deceleration of a Poynting flux-dominated flow. X-ray flares suggest that the GRB central engine is very likely still active after the prompt gamma-ray emission is over, but with a reduced activity at later times. In some cases, the central engine activity even extends to days after the burst triggers. Analyses of early X-ray afterglow data reveal that GRBs are indeed highly relativistic events and that early afterglow data of many bursts, starting from the beginning of the XRT observations, are consistent with the afterglow emission from an ISM environment.