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arXiv 1706.09896astro-ph.HE
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偏心Kozai-Lidov效应引起的星系核黑洞合并

Black Hole Mergers in Galactic Nuclei Induced by the Eccentric Kozai-Lidov Effect

Bao-Minh Hoang, Smadar Naoz, Bence Kocsis, Frederic A. Rasio, Fani Dosopoulou

摘要:

大质量黑洞周围的核星团预计将大量存在恒星质量黑洞和黑洞双星。这些双星形成了一个以大质量黑洞为中心的三重系统。来自大质量黑洞的引力扰动能引起高偏心率激发。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,以至于引力波发射驱动双星合并。在本文中,我们考虑一个简单的概念证明,并探讨偏心Kozai-Lidov机制不等质量双星的效果。我们用蒙特卡罗模拟方法模拟了在四极和八极长期扰动、广义相对论进动和引力波辐射下星系核中的BH-BH双星。对于标称数量的稳态BH-BH二进制文件,我们的模型给出了一个总的合并率$\sim 1 - 3$ $Gpc^{-3} yr^{-1}$,这取决于假设的密度分布。因此,我们的模型可能与其他动力学机制,如在球状星团或致密的核集群没有一个大规模的黑洞的BH双星的动力学形成和合并的竞争。我们提供了这些LIGO源在星系核的分布预测。

英文摘要:

Nuclear star clusters around massive black holes are expected to be abundant in stellar mass black holes and black hole binaries. These binaries form a hierarchical triple system with the massive black hole at the center. Gravitational perturbations from the massive black hole can cause high eccentricity excitation. During this process, the eccentricity may approach unity, and the pericenter distance may become sufficiently small that gravitational wave emission drives the binary to merge. In this paper, we consider a simple proof of concept and explore the effect of the eccentric Kozai-Lidov mechanism for unequal mass binaries. We perform a set of Monte Carlo simulations on BH-BH binaries in galactic nuclei with quadrupole and octupole-level secular perturbations, general relativistic precession, and gravitational wave emission. For a nominal number of steady-state BH-BH binaries, our model gives a total merger rate $\sim 1 - 3$$Gpc^{-3} yr^{-1}$, depending on the assumed density profile. Thus, our model potentially competes with other dynamical mechanisms, such as the dynamical formations and mergers of BH binaries in globular clusters or dense nuclear clusters without a massive black hole. We provide predictions for the distributions of these LIGO sources in galactic nuclei.

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