Black Hole Mergers in Galactic Nuclei Induced by the Eccentric Kozai–Lidov Effect
Black Hole Mergers in Galactic Nuclei Induced by the Eccentric Kozai–Lidov Effect
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DOI：
10.3847/1538-4357/aaafce
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发表时间：
2017-06
期刊：
影响因子：
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通讯作者：
Bao-Minh Hoang;S. Naoz;B. Kocsis;F. Rasio;F. Dosopoulou
中科院分区：
文献类型：
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作者：
Bao-Minh Hoang;S. Naoz;B. Kocsis;F. Rasio;F. Dosopoulou
中心大质量黑洞周围的核星星团中可能存在大量的恒星黑洞遗迹和黑洞-黑洞双星。这些双星与中心MBH形成一个分层的三重系统，来自MBH的引力摄动可以在BH-BH双星轨道中引起高偏心率的激发。在这个过程中，偏心率可能接近1，近心距离可能变得足够小，以至于引力波辐射驱动BH-BH双星合并。在这项工作中，我们为这个过程构建了一个简单的概念验证模型，具体来说，我们研究了不等质量软BH-BH双星中的偏心Kozai-Lidov机制。我们的模型是基于一组Monte Carlo模拟银河核中的BH-BH双星，考虑到四极和八极水平的长期扰动，广义相对论进动，和引力波发射。对于一个典型的稳态数目的BH-BH双星，我们的模型预测总的合并速率为101 -3 −3 −1，这取决于假设的原子核密度分布。因此，我们的机制可能会与其他动力学形成过程的合并BH-BH双星，如在球状星团或在核星星集群没有MBH恒星BH的相互作用竞争。
Nuclear star clusters around a central massive black hole (MBH) are expected to be abundant in stellar black hole (BH) remnants and BH–BH binaries. These binaries form a hierarchical triple system with the central MBH, and gravitational perturbations from the MBH can cause high-eccentricity excitation in the BH–BH binary orbit. During this process, the eccentricity may approach unity, and the pericenter distance may become sufficiently small so that gravitational-wave emission drives the BH–BH binary to merge. In this work, we construct a simple proof-of-concept model for this process, and specifically, we study the eccentric Kozai–Lidov mechanism in unequal-mass, soft BH–BH binaries. Our model is based on a set of Monte Carlo simulations for BH–BH binaries in galactic nuclei, taking into account quadrupole- and octupole-level secular perturbations, general relativistic precession, and gravitational-wave emission. For a typical steady-state number of BH–BH binaries, our model predicts a total merger rate of ∼1–3 −3 −1, depending on the assumed density profile in the nucleus. Thus, our mechanism could potentially compete with other dynamical formation processes for merging BH–BH binaries, such as the interactions of stellar BHs in globular clusters or in nuclear star clusters without an MBH.