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arXiv 1708.07008astro-ph.HEgr-qc
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短伽玛暴:张开角、局域中子星合并率和GRB/GW协的离轴事件

Short GRBs: opening angles, local neutron star merger rate and off-axis events for GRB/GW association

Zhi-Ping Jin, Xiang Li, Hao Wang, Yuan-Zhu Wang, Hao-Ning He, Qiang Yuan, Fu-Wen Zhang, Yuan-Chuan Zou, Yi-Zhong Fan, Da-Ming Wei

摘要:

短伽玛射线暴(SGRB)余辉光变曲线中的喷流中断,迄今为止很少被探测到,对于估算喷出物的半张角($θ_{\rm j}$)和中子星合并率至关重要。在这项工作中,我们报告了GRB 150424 A和GRB 160821 B的喷流下降行为的检测,并发现$θ_{\rm j}\sim 0.1$ rad。加上2015年之前报告的5个事件和最近“确定”的另外3个事件(GRB 050709、GRB 060614和GRB 140903 A),我们有一个由9个SGRB和1个长短GRB组成的样本,并合理估计了$θ_{\rm j}$。特别是,样本中的三个{ \it Swift}爆发具有红移$z\leq 0.2$,我们用它估计本地中子星合并率密度{为$\sim 1109^{+1432}_{-657}~{\rm Gpc^{-3}~yr^{-1}}$或$162^{+140}_{-83} {\rm Gpc^{-3}yr^{-1}}$,如果排除窄束GRB 061201}。受目前发现的典型$θ_{\rm j}\sim 0.1$ rad的启发,我们进一步研究了离束GRB(均匀喷流模型)或离轴事件(结构喷流模型)是否能显著增强GRB/GW关联。对于前者,增强最多是中等的,而对于后者,增强可以大得多,并且$\sim 10\%$的高GRB/GW关联概率是可能的。我们还表明,GRB 160821 B的数据可能包含一个macronova/kilonova发射组件的温度为$\sim 3100$ K在$\sim 3.6$天后爆发和更多的数据,需要最终澄清。

英文摘要:

The jet breaks in the afterglow lightcurves of short gamma-ray bursts (SGRBs), rarely detected so far, are crucial for estimating the half-opening angles of the ejecta ($θ_{\rm j}$) and hence the neutron star merger rate. In this work we report the detection of jet decline behaviors in GRB 150424A and GRB 160821B and find $θ_{\rm j}\sim 0.1$ rad. Together with five events reported before 2015 and other three "identified" recently (GRB 050709, GRB 060614 and GRB 140903A), we have a sample consisting of nine SGRBs and one long-short GRB with reasonably estimated $θ_{\rm j}$. In particular, three {\it Swift} bursts in the sample have redshifts $z\leq 0.2$, with which we estimate the local neutron star merger rate density {to be $\sim 1109^{+1432}_{-657}~{\rm Gpc^{-3}~yr^{-1}}$ or $162^{+140}_{-83} {\rm Gpc^{-3}yr^{-1}}$ if the narrowly-beamed GRB 061201 is excluded}. Inspired by the typical $θ_{\rm j}\sim 0.1$ rad found currently, we further investigate whether the off-beam GRBs (in the uniform jet model) or the off-axis events (in the structured jet model) can significantly enhance the GRB/GW association or not. For the former the enhancement is at most moderate, while for the latter the enhancement can be much greater and a high GRB/GW association probability of $\sim 10\%$ is possible. We also show that the data of GRB 160821B may contain a macronova/kilonova emission component with a temperature of $\sim 3100$ K at $\sim 3.6$ days after the burst and more data are needed to ultimately clarify.

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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