双高斯喷流结构及其形成过程:来自GRB 170817A余辉的限制  

The two-Gaussian jet structure and its formation process:Constraints from the afterglows of GRB 170817A

作　　者：魏芳 张震东 俞云伟[1] 刘良端 WEI Fang;ZHANG Zhen-Dong;YU Yun-Wei;LIU Liang-Duan(Institute of Astrophysics,Central China Normal University,Wuhan 430079,China)

机构地区：[1]华中师范大学天体物理研究所,武汉430079

出　　处：《中国科学：物理学、力学、天文学》2022年第12期152-161,共10页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家重点基础研究发展计划(编号:2021YFA0718500);国家自然科学基金(编号:11822302,11833003)资助项目。

摘　　要：短时标伽马射线暴(简称短暴)GRB 170817A是人类发现的第一个与引力波事件成协的伽马暴,为深入研究短暴的发生机制提供了宝贵的机会,其中它的多波段余辉辐射很可能展示了喷流的角向结构.而有关短暴的大样本统计研究表明,如果用高斯函数来唯象描述喷流结构,很可能需要引入两个高斯函数才能够把GRB170817A的辐射和其他普通的短暴统一起来.换言之,GRB 170817A的瞬时辐射很可能来自具有更大张角的额外喷流成分.因此,为了检验这种双高斯喷流结构和GRB 170817A余辉数据的相容性,本文计算了该喷流结构在偏轴观测下的多波段余辉,发现外高斯成分的引入能够很好地解释GRB 170817A余辉数据的早期上扬趋势.在此基础上,我们还计算了喷流在并合抛射物中的传播和突破过程,表明这些过程可以自然导致观测限制所得的双高斯喷流结构,从而展现出了模型的整体自洽性.此外,对喷流传播过程的观测限制也为我们了解并合抛射物的性质提供了新的线索.The short gamma-ray burst(SGRB)GRB 170817A was the first observed GRB associated with a gravitational-wave event,providing a valuable opportunity to further study the producing mechanism of SGRBs.Its multi-wavelength afterglow emissions probably reveal the angular structure of the jet to us.And,if the jet structure is described phenomenologically by a Gaussian function,large sample statistical studies on SGRBs show that we probably need to introduce two-Gaussian functions to unify the emissions from GRB 170817A with other normal SGRBs.In other words,GRB 170817A’s prompt emission is likely from an additional component of a jet with a larger angle.Therefore,in order to test the compatibility between this two-Gaussian jet structure and the afterglow data of GRB 170817A,we calculate the multi-wavelength afterglow light curves from such an off-axis jet structure,and find that the introduction of the outer Gaussian component can well explain the early uptrend of the GRB 170817A afterglow data.On this basis,we also calculate the propagation and breakout processes of the jet in the merger ejecta,which shows that these processes can naturally lead to the two-Gaussian jet structure obtained by the observational constraint,thus showing the overall self-consistency of the model.Furthermore,the observational constraint on the jet propagation process also provides a new clue for understanding the properties of merger ejecta.

关 键 词：伽马射线暴 GRB喷流 引力波 

分 类 号：P172.3[天文地球—天文学] P142.84