General-relativistic neutrino-radiation magnetohydrodynamic simulation of seconds-long black hole-neutron star mergers
General-relativistic neutrino-radiation magnetohydrodynamic simulation of seconds-long black hole-neutron star mergers
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DOI：
10.1103/physrevd.106.023008
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发表时间：
2021-11
影响因子：
5
通讯作者：
Kota Hayashi;S. Fujibayashi;K. Kiuchi;K. Kyutoku;Y. Sekiguchi;M. Shibata
中科院分区：
文献类型：
--
作者：
Kota Hayashi;S. Fujibayashi;K. Kiuchi;K. Kyutoku;Y. Sekiguchi;M. Shibata
首次对黑洞-中子星星合并进行了秒级数值相对论模拟，得到了黑洞-中子星合并过程及合并后演化过程的自洽图像。为了研究潮汐扰动发生的情况，我们选择黑洞的初始质量为5.4M_\odot $或8.1M_\odot $，无量纲自旋为0.75。中子星的质量被固定为1.35M_odot $。我们发现，在潮汐破裂后，动力学质量喷射发生花费$\lesssim 10$ ms的巨大的吸积盘的形成。随后，磁盘中的磁场被磁绕组和磁旋转不稳定性放大，建立湍流状态并诱导角动量输运。磁致粘性效应引起的合并后物质抛射在潮汐破裂后的300 - 500毫秒处开始，此时中微子的光度降到10^{51.5}，在物质和磁通量从黑洞落入黑洞后，黑洞旋转轴附近的磁层发展起来。吸积盘，高强度坡印廷通量产生集在几百毫秒后的潮汐中断。在合并后的物质抛射之后，由于磁层张角的增大，坡印亭通量的强度变低。具有强坡印亭通量的阶段的寿命为$1$-2 s，这与短硬伽马射线暴的典型持续时间一致。
Seconds-long numerical-relativity simulations for black hole-neutron star mergers are performed for the first time to obtain a self-consistent picture of the merger and post-merger evolution processes. To investigate the case that tidal disruption takes place, we choose the initial mass of the black hole to be $5.4M_\odot$ or $8.1M_\odot$ with the dimensionless spin of 0.75. The neutron-star mass is fixed to be $1.35M_\odot$. We find that after the tidal disruption, dynamical mass ejection takes place spending $\lesssim 10$ ms together with the formation of a massive accretion disk. Subsequently, the magnetic field in the disk is amplified by the magnetic winding and magnetorotational instability, establishing a turbulent state and inducing the angular momentum transport. The post-merger mass ejection by the magnetically-induced viscous effect sets in at $\sim 300$-500\,ms after the tidal disruption, at which the neutrino luminosity drops below $\sim 10^{51.5}\,{\rm erg/s}$, and continues for several hundreds ms. A magnetosphere near the rotational axis of the black hole is developed after the matter and magnetic flux fall into the black hole from the accretion disk, and high-intensity Poynting flux generation sets in at a few hundreds ms after the tidal disruption. The intensity of the Poynting flux becomes low after the significant post-merger mass ejection, because the opening angle of the magnetosphere increases. The lifetime for the stage with the strong Poynting flux is $1$-2 s, which agrees with the typical duration of short-hard gamma-ray bursts.