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arXiv 2012.12036astro-ph.HE
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伽玛暴中的巨X射线和光学凸点:后退吸积模型的证据

Giant X-ray and optical Bump in GRBs: evidence for fall-back accretion model

Litao Zhao, He Gao, WeiHua Lei, Lin Lan, Liangduan Liu

摘要:

专用探测器的成功运行为我们了解伽马射线暴(GRB)的中心引擎和起源提供了有价值的信息。例如,在一些长持续时间的伽玛暴(如伽玛暴121027 A和111209 A)中发现的巨大的X射线和光学凸起意味着一些扩展的中央发动机活动,如晚期的X射线耀斑,可能是由于祖先包层材料的回落。在这里,我们系统地搜索长伽玛暴,包括一个巨大的X射线或光学凹凸从雨燕伽玛暴样品,最终我们发现19个新的可能的候选人。在合理的参数范围内,后退吸积模型可以很好地解释所有候选粒子的X射线和光学凸块。6个候选者同时显示出在X射线和光学观测中的撞击特征,当将X射线通量按比例缩小到光学一个数量级时,这些特征可以同时很好地拟合,与标准的$F_ν\proptoν^{1/3}$同步加速器光谱一致。典型的后退半径分布在$10^{10}\rm-10^{12}$ cm左右,这与沃尔夫-拉叶星的典型半径一致。在时间$\sim10^{2}- 10^{5}~\rm s$,峰值回落吸积率在$\sim 10^{-11}-10^{-4}M_{\odot} \ \text{s} ^{-1}$的范围内,这是相对容易实现的,只要祖先的金属丰度不是太高。结合我们发现的样本,进一步研究不同质量、金属丰度和角动量分布的母源的质量供给率将有助于我们更好地约束长伽玛暴的母源性质。

英文摘要:

The successful operation of dedicated detectors has brought us valuable information for understanding the central engine and the progenitor of gamma-ray bursts (GRBs). For instance, the giant X-ray and optical bumps found in some long-duration GRBs (e.g. GRBs 121027A and 111209A) imply that some extended central engine activities, such as the late X-ray flares, are likely due to the fall-back of progenitor envelope materials. Here we systemically search for long GRBs that consist of a giant X-ray or optical bump from the Swift GRB sample, and eventually we find 19 new possible candidates. The fall-back accretion model could well interpret the X-ray and optical bump for all candidates within a reasonable parameter space. Six candidates showing simultaneous bump signatures in both X-ray and optical observations, which could be well fitted at the same time when scaling down the X-ray flux into optical by one order of magnitude, are consistent with the standard $F_ν\proptoν^{1/3}$ synchrotron spectrum. The typical fall-back radius is distributed around $10^{10}\rm-10^{12}$ cm, which is consistent with the typical radius of a Wolf-Rayet star. The peak fall-back accretion rate is in the range of $\sim 10^{-11}-10^{-4}M_{\odot} \ \text{s} ^{-1}$ at time $\sim10^{2}- 10^{5}~\rm s$, which is relatively easy to fulfill as long as the progenitor's metallicity is not too high. Combined with the sample we found, future studies of the mass supply rate for the progenitors with different mass, metallicity, and angular momentum distribution would help us to better constrain the progenitor properties of long GRBs.

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。

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