The Shallow Decay Segment of GRB X-Ray Afterglow Revisited
The Shallow Decay Segment of GRB X-Ray Afterglow Revisited
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重新审视 GRB X 射线余辉的浅衰变部分
DOI：
10.3847/1538-4357/ab38c4
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Zhang Bing
中科院分区：
文献类型：
--
作者：
Zhao Li-Tao;Zhang Bin-Bin;Gao He;Lan Lin;Lv Houjun;Zhang Bing
基于Neil GehrelsSwift天文台早些时候的观测，梁等人。对伽马射线暴(GRBs)X射线余辉的浅衰变分量进行了系统的分析，以探索其物理来源。在这里，我们使用更新的样本(使用2004年2月至2017年7月期间的SWIFT/XRT GRBs)重新审视分析。我们发现，随着样本的增加，(1)浅层衰变相(如Tb、SX、ΓX、1和αX，1)的特征性质的分布仍然服从正态或对数正态分布；(2)ΓX、1和Γγ仍然不存在相关性，但伽马射线相和X射线相之间的持续时间、能量通量和各向同性能量的暂定关联仍然存在；(3)对于大多数伽玛暴，浅衰变段与其后续段之间没有显著的谱演化，后者通常与外部激波模型相一致；(4)假设中心引擎的光度释放历史为幂函数，我们发现Q值主要分布在−0.5~0.5之间，平均值为0.16±0.12；(5)与之间的试探性相关消失，全球三参数相关()变得不那么显著；(6)LX和与三参数相关()之间的反相关确实存在，并具有较高的置信度。总体而言，我们的结果与梁等人的结果基本一致，证实了他们的观点，即大多数爆发中的浅衰变部分与外部前向激波来源是一致的，这可能是由于长寿命中央引擎的持续能量注入。
Based on the early-year observations from Neil Gehrels Swift Observatory, Liang et al. performed a systematic analysis for the shallow decay component of gamma-ray bursts (GRBs) X-ray afterglow, in order to explore its physical origin. Here we revisit the analysis with an updated sample (with Swift/XRT GRBs between 2004 February and 2017 July). We find that with a larger sample, (1) the distributions of the characteristic properties of the shallow decay phase (e.g., tb, SX, ΓX,1, and αX,1) still accord with normal or lognormal distribution; (2) ΓX,1 and Γγ still show no correlation, but the tentative correlations of durations, energy fluences, and isotropic energies between the gamma-ray and X-ray phases still exist; (3) for most GRBs, there is no significant spectral evolution between the shallow decay segment and its follow-up segment, and the latter is usually consistent with the external-shock models; (4) assuming that the central engine has a power-law luminosity release history as , we find that the value q is mainly distributed between −0.5 and 0.5, with an average value of 0.16 ± 0.12; (5) the tentative correlation between and disappears, so that the global three-parameter correlation ( ) becomes less significant; (6) the anticorrelation between LX and and the three-parameter correlation ( ) indeed exist with a high confidence level. Overall, our results are generally consistent with Liang et al., confirming their suggestion that the shallow decay segment in most bursts is consistent with an external forward shock origin, probably due to a continuous energy injection from a long-lived central engine.