Detailed polarization measurements of the prompt emission of five gamma-ray bursts
Detailed polarization measurements of the prompt emission of five gamma-ray bursts
复制标题
五次伽马射线暴瞬时发射的详细偏振测量
DOI：
10.1038/s41550-018-0664-0
复制
发表时间：
2019-03-01
期刊：
影响因子：
14.1
通讯作者：
Shi, Hao-Li
中科院分区：
文献类型：
--
作者：
Zhang, Shuang-Nan;Kole, Merlin;Shi, Hao-Li
伽马射线暴(GRB)是自大爆炸以来宇宙中最强的爆炸。它们被认为是在大质量恒星演化结束时黑洞的形成(1-3)或致密天体的合并(4)中产生的。伽玛暴的光谱和时间特性表明，观测到的明亮伽马射线是在宇宙中最相对论的喷流中产生的(4)；然而，尽管进行了几十年的研究，这些喷流的物理特性(特别是结构和磁拓扑结构)仍然不是很清楚。人们普遍认为，对伽玛暴偏振特性的精确测量应该提供关于高度相对论喷流的关键信息(5)。因此，已经有许多关于伽玛暴偏振测量的报告，结果各不相同(参见参考文献)。(6))；然而，许多这样的测量存在很大的不确定性，其中大多数是系统性的(参考文献)。(7)及其所指的事项)。在用伽马射线暴偏振仪(GAP)和康普顿光谱仪和成像仪(COSI)首次成功测量(8-10)之后，我们报告了一个具有统计意义的精确偏振测量样本，它是由中国的天宫二号空间实验室上的专用伽马射线暴偏振计极地获得的。我们的结果表明，尽管我们的结果也显示了偏振角的脉内演化，但伽马射线发射的最大偏振水平低于一些流行模型预测的水平。这表明，低偏振度可能是由于伽玛暴过程中偏振角的演化所致。
Gamma-ray bursts (GRBs) are the strongest explosions in the Universe since the Big Bang. They are believed to be produced either in the formation of black holes at the end of massive star evolution(1-3) or the merging of compact objects(4). Spectral and timing properties of GRBs suggest that the observed bright gamma-rays are produced in the most relativistic jets in the Universe(4); however, the physical properties (especially the structure and magnetic topologies) of the jets are still not well known, despite several decades of studies. It is widely believed that precise measurements of the polarization properties of GRBs should provide crucial information on the highly relativistic jets(5). As a result, there have been many reports of GRB polarization measurements with diverse results (see ref. (6)); however, many such measurements suffer from substantial uncertainties, most of which are systematic (ref. (7) and the references therein). After the first successful measurements by the Gamma-Ray Burst Polarimeter (GAP) and Compton Spectrometer and Imager (COSI) instruments(8-10), here we report a statistically meaningful sample of precise polarization measurements, obtained with the dedicated GRB polarimeter POLAR onboard China's Tiangong-2 space laboratory. Our results suggest that the gamma-ray emission is at most polarized at a level lower than some popular models have predicted, although our results also show intrapulse evolution of the polarization angle. This indicates that the low polarization degrees could be due to an evolving polarization angle during a GRB.