Binary neutron star mergers and short gamma-ray bursts: Effects of magnetic field orientation, equation of state, and mass ratio
Binary neutron star mergers and short gamma-ray bursts: Effects of magnetic field orientation, equation of state, and mass ratio
复制标题
双中子星合并和短伽马射线暴：磁场方向、状态方程和质量比的影响
DOI：
10.1103/physrevd.94.064012
复制
发表时间：
2016
影响因子：
5
通讯作者：
Rosalba
中科院分区：
文献类型：
--
作者：
Kawamura;Takumu; Giacomazzo;Bruno; Kastaun;Wolfgang; Ciolfi;Riccardo; Endrizzi;Andrea; Baiotti;Luca; Perna;Rosalba
我们提出了双中子星（BNS）系统合并的完全广义相对论磁流体动力学模拟。我们认为 BNS 会产生一颗超大质量中子星 (HMNS)，在几十毫秒内坍缩成一个被磁化吸积盘包围的旋转黑洞 (BH)。我们研究此类系统是否可以发射相对论性喷流，从而为短伽马射线爆发提供动力。我们研究不同状态方程 (EOS)、不同质量比和不同磁场方向的影响。对于所有情况，我们对物质动力学和磁场演化进行了详细的研究，特别关注其整体结构和相对论喷流的可能发射。这项工作的主要结果是我们观察到有组织的磁场结构的形成。这种情况的发生与 EOS、质量比和初始磁场方向无关。我们还表明，那些产生寿命较长的 HMNS 的模型会在塌陷到 BH 之前产生更强的磁场。对于我们的至少一个模型来说，这种更大的磁场使得解决磁旋转不稳定性成为可能，从而进一步放大磁盘中的磁场。然而，在模拟结束时，我们（尚未）观察到磁控漏斗或相对论流出。关于 Ruizet al.[天体物理学。 J. 824, L6 (2016)]，我们演化出具有更低且更合理的初始磁场强度的模型，并且（出于计算原因）我们没有演化出吸积盘的长时间尺度，而这似乎是观察相对论流出所需的。由于我们所有的模型都会产生与 BH 自旋轴对齐的类似有序磁场结构，因此我们预计 Ruizet 等人（仅考虑具有理想流体 EOS 的等质量系统）发现的结果应该是通用的，并且至少从定性的角度来看，与质量比、磁场方向和 EOS 无关。
We present fully general-relativistic magnetohydrodynamic simulations of the merger of binary neutron star (BNS) systems. We consider BNSs producing a hypermassive neutron star (HMNS) that collapses to a spinning black hole (BH) surrounded by a magnetized accretion disk in a few tens of ms. We investigate whether such systems may launch relativistic jets and hence power short gamma-ray bursts. We study the effects of different equations of state (EOSs), different mass ratios, and different magnetic field orientations. For all cases, we present a detailed investigation of the matter dynamics and of the magnetic field evolution, with particular attention to its global structure and possible emission of relativistic jets. The main result of this work is that we observe the formation of an organized magnetic field structure. This happens independently of EOS, mass ratio, and initial magnetic field orientation. We also show that those models that produce a longer-lived HMNS lead to a stronger magnetic field before collapse to a BH. Such larger fields make it possible, for at least one of our models, to resolve the magnetorotational instability and hence further amplify the magnetic field in the disk. However, by the end of our simulations, we do not (yet) observe a magnetically dominated funnel nor a relativistic outflow. With respect to the recent simulations of Ruizet al.[Astrophys. J. 824, L6 (2016)], we evolve models with lower and more plausible initial magnetic field strengths and (for computational reasons) we do not evolve the accretion disk for the long time scales that seem to be required in order to see a relativistic outflow. Since all our models produce a similar ordered magnetic field structure aligned with the BH spin axis, we expect that the results found by Ruizet al.(who only considered an equal-mass system with an ideal fluid EOS) should be general and—at least from a qualitative point of view—independent of the mass ratio, magnetic field orientation, and EOS.