arXiv 0705.13732007-05astro-ph

Swift/XRT数据的综合分析：II。浅衰变段的不同物理起源

A Comprehensive Analysis of the Swift/XRT Data: II. Diverse Physical Origins of the Shallow Decay Segment

En-Wei Liang, Bin-Bin Zhang, Bing Zhang

备注：: 27 pages in emulateapj style, 8 figures, accepted for publication in ApJ, optical data fitting and references added, conclusions unchanged. This is the second paper of a series. Paper I see astro-ph/0612246 (ApJ, 2007, in press)
DOI：: 10.1086/521870

摘要：

我们分析了53个长的雨燕伽玛暴样品的浅衰变段的性质。结果表明，其特征分布为对数正态或正态分布，各向同性X射线能量（E_{iso,X}）与瞬发γ射线能量线性相关，但除某些X射线闪光外，其光子谱较陡。从这一阶段到后续阶段没有观察到显著的光谱演变，并且后续阶段通常与外部冲击模型一致，这意味着这一段可能是由于更新的外部冲击。在这种情况下，数据通常与大致恒定的注入光度一致，直到该阶段$t_b$结束。E_{iso, X}和t_b之间的正相关也有利于这种情况。在13个光学光变曲线采样良好的爆发中，有6个爆发在tb附近出现了光学突变，并且这些突变与消色差一致。然而，其他7个爆发或者没有显示出光学破裂，或者在与t_b不同的时期具有破裂。这引起了对能量注入场景的关注，表明光学和X射线发射可能不是相同的分量，至少对于一小部分爆发。在样本中有4个显著的异常值，并且在这些爆发中的这个浅的decau阶段之后紧接着是tb之后的非常陡峭的衰减，这与任何外部冲击模型都不一致。这些爆发的光学数据独立于X射线数据。这些X射线平台可能有一个内部的起源，并要求连续运行的长期伽玛射线暴中央引擎。我们的结论是，观察到的浅衰变阶段可能有不同的物理起源（摘要）。

英文摘要：

We analyze the properties of the shallow decay segment with a sample of 53 long Swift GRBs. We show that the distributions of its characteristics are log-normal or normal, and its isotropic X-ray energy (E_{iso,X}) is linearly correlated with the prompt gamma-ray energy, but with a steeper photon spectrum except for some X-ray flashes. No significant spectral evolution is observed from this phase to the follow-up phase, and the follow-up phase is usually consistent with the external shock models, implying that this segment likely due to a refreshed external shock. Within this scenario, the data are generally consistent with a roughly constant injection luminosity up to the end of this phase $t_b$. A positive correlation between E_{iso, X} and t_b also favors this scenario. Among the 13 bursts that have well-sampled optical light curves, 6 have an optical break around t_b and the breaks are consistent with being achromatic. However, the other 7 bursts either do not show an optical break or have a break at a different epoch than t_b. This raises a concern to the energy injection scenario, suggesting that the optical and X-ray emissions may not be the same component at least for a fraction of bursts. There are 4 significant outliers in the sample, and this shallow decau phase in these bursts is immediately followed by a very steep decay after t_b, which is inconsistent with any external shock model. The optical data of these bursts evolve independently from the X-ray data. These X-ray plateaus likely have an internal origin and demand continuous operation of a long-term GRB central engine. We conclude that the observed shallow decay phase likely has diverse physical origins(Abridged).

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

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