论文标题
是什么决定了短伽马射线爆发喷气机的结构?
What determines the structure of short gamma-ray burst jets?
论文作者
论文摘要
GRB 170817a的发现,这是由中子星合并引起的第一个明确的离轴短伽玛射线爆发,它挑战了我们对相对主义喷射的角度结构的理解。对射流传播的研究通常假设射流是从中央发动机弹出的,其最终结构及其最终结构(决定了观察到的光曲线和光谱)主要受与附近环境的相互作用的调节。但是,如全球积聚模拟所示,预计喷气机的结构比简单的顶部帽子更复杂。我们介绍了启动的短GRB的数值模拟,并具有广泛的初始结构,持续时间和亮度。我们遵循与合并残留风的喷气机相互作用,并在距离中央发动机的距离$ \ gtrsim 10^{11} $ cm处计算其最终结构。我们表明,最终的射流结构以及由此产生的余辉发射在很大程度上取决于射流的初始结构,其发光度和持续时间。虽然射流的初始结构可用于持久的SGRB,但对喷气机几乎没有通过风的方式进行了强烈修改。这说明了将全球模拟结果与传播研究结果相结合的重要性,以便更好地预测中子星合并的预期余辉签名。结构化的喷气机提供了GRB 170817a余辉发射的合理描述,其轴向角度$θ_ {\ rm obs} \大约22.5^\ circ $。
The discovery of GRB 170817A, the first unambiguous off-axis short gamma-ray burst arising from a neutron star merger, has challenged our understanding of the angular structure of relativistic jets. Studies of the jet propagation usually assume that the jet is ejected from the central engine with a top-hat structure and its final structure, which determines the observed light curve and spectra, is primarily regulated by the interaction with the nearby environment. However, jets are expected to be produced with a structure that is more complex than a simple top-hat, as shown by global accretion simulations. We present numerical simulations of short GRBs launched with a wide range of initial structures, durations and luminosities. We follow the jet interaction with the merger remnant wind and compute its final structure at distances $\gtrsim 10^{11}$~cm from the central engine. We show that the final jet structure, as well as the resulting afterglow emission, depend strongly on the initial structure of the jet, its luminosity and duration. While the initial structure at the jet is preserved for long-lasting SGRBs, it is strongly modified for jets barely making their way through the wind. This illustrates the importance of combining the results of global simulations with propagation studies in order to better predict the expected afterglow signatures from neutron star mergers. Structured jets provide a reasonable description of the GRB 170817A afterglow emission with an off-axis angle $θ_{\rm obs} \approx 22.5^\circ$.