论文标题
发动机和喷气机的固有特性为与GW170817相关的短伽马射线爆发供电
Intrinsic properties of the engine and jet that powered the short gamma-ray burst associated with GW170817
论文作者
论文摘要
GRB 170817a是一种从二进制中子星（BNS）合并的重力波信号GW170817后检测到的高含量短伽马射线爆发。现在，它被理解为一个离轴事件，该事件由相对论喷射的茧驱动，距离观察方向为15至30度。茧通过从合并残留物中的非偏见性巴里昂风与非相关性的重子风的相互作用进行了通电，从而导致带有狭窄的芯子和宽阔的机翼的结构性流出。在本文中，我们将结构化流出的观察性约束与喷气风相互作用的模型相结合，以限制中央发动机启动喷气机的内在属性，包括其从合并事件中的时间延迟。使用受磁化BNS合并模拟启发的风处方，我们发现该喷射是从合并开始在约0.4 s内发射的，这意味着1.74 s观察到的延迟是由火球传播到光球半径的主导。我们还首次限制了任何伽马射线爆发，即注射处的射流开头，并将下限设置为其渐近洛伦兹因子。这些发现表明，最初是通过电磁工艺发射的Poynting-Flux主导的喷气机。如果射流是通过积聚的黑洞供电的，则它们还对亚稳态中子恒星残留物的生存时间提供了重大限制。
GRB 170817A was a subluminous short gamma-ray burst detected about 1.74 s after the gravitational wave signal GW170817 from a binary neutron star (BNS) merger. It is now understood as an off-axis event powered by the cocoon of a relativistic jet pointing 15 to 30 degrees away from the direction of observation. The cocoon was energized by the interaction of the incipient jet with the non-relativistic baryon wind from the merger remnant, resulting in a structured outflow with a narrow core and broad wings. In this paper, we couple the observational constraints on the structured outflow with a model for the jet-wind interaction to constrain the intrinsic properties with which the jet was launched by the central engine, including its time delay from the merger event. Using wind prescriptions inspired by magnetized BNS merger simulations, we find that the jet was launched within about 0.4 s from the merger, implying that the 1.74 s observed delay was dominated by the fireball propagation up to the photospheric radius. We also constrain, for the first time for any gamma-ray burst, the jet opening angle at injection and set a lower limit to its asymptotic Lorentz factor. These findings suggest an initially Poynting-flux dominated jet, launched via electromagnetic processes. If the jet was powered by an accreting black hole, they also provide a significant constraint on the survival time of the metastable neutron star remnant.
