Numerical simulations of neutron star-black hole binaries in the near-equal-mass regime
Numerical simulations of neutron star-black hole binaries in the near-equal-mass regime
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DOI：
10.1103/physrevd.99.103025
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发表时间：
2019-03
影响因子：
5
通讯作者：
F. Foucart;Matthew D. Duez;Lawrence E. Kidder;S. Nissanke;H. Pfeiffer;M. Scheel
中科院分区：
文献类型：
--
作者：
F. Foucart;Matthew D. Duez;Lawrence E. Kidder;S. Nissanke;H. Pfeiffer;M. Scheel
对中子星-黑洞(NSBH)双星的模拟通常考虑质量在$(5-10)M_\ODOT$范围内的黑洞，我们期望在那里找到最大恒星质量的黑洞。然而，理论上不能排除低质量黑洞的存在。在有中子星伴星的双星系统中，小质量黑洞可以模拟中子星-中子(NSNS)双星，因为它们提供类似的引力波(GW)和电磁(EM)信号。为了了解NSNS合并和低质量NSBH合并之间的区别和相似之处，需要进行数值模拟。在这里，我们执行一组低质量NSBH合并的模拟，包括与GW170817兼容的系统。我们的模拟使用了与成分和温度相关的状态方程(DD2)和近似的中微子输运，但没有使用磁场。我们发现，低质量的NSBH合并产生的剩余盘质量明显小于之前的预期，并且与从GW170817推断的适度不对称质量比合并后的流出质量一致。与GW170817兼容的系统产生的动力学抛射可以忽略不计，除非质量比和黑洞自转处于允许的参数空间的边缘。这种动态喷发是冷的、富含中子的，对于中子星潮汐破裂时产生的喷发来说，速度惊人地慢：$v\sim(0.1-0.15)c$。我们还发现，残存黑洞的最终质量与现有的分析预测是一致的，而该黑洞的最终自转明显大于预期--在我们同等质量的情况下，最高可达$\chi_{\rm BH}=0.84$。
Simulations of neutron star-black hole (NSBH) binaries generally consider black holes with masses in the range $(5-10)M_\odot$, where we expect to find most stellar mass black holes. The existence of lower mass black holes, however, cannot be theoretically ruled out. Low-mass black holes in binary systems with a neutron star companion could mimic neutron star-neutron (NSNS) binaries, as they power similar gravitational wave (GW) and electromagnetic (EM) signals. To understand the differences and similarities between NSNS mergers and low-mass NSBH mergers, numerical simulations are required. Here, we perform a set of simulations of low-mass NSBH mergers, including systems compatible with GW170817. Our simulations use a composition and temperature dependent equation of state (DD2) and approximate neutrino transport, but no magnetic fields. We find that low-mass NSBH mergers produce remnant disks significantly less massive than previously expected, and consistent with the post-merger outflow mass inferred from GW170817 for moderately asymmetric mass ratio. The dynamical ejecta produced by systems compatible with GW170817 is negligible except if the mass ratio and black hole spin are at the edge of the allowed parameter space. That dynamical ejecta is cold, neutron-rich, and surprisingly slow for ejecta produced during the tidal disruption of a neutron star : $v\sim (0.1-0.15)c$. We also find that the final mass of the remnant black hole is consistent with existing analytical predictions, while the final spin of that black hole is noticeably larger than expected -- up to $\chi_{\rm BH}=0.84$ for our equal mass case.