Do three-body encounters in galactic nuclei affect compact binary merger rates?

Abstract

High-density cusps of compact remnants are expected to form around supermassive black holes (SMBHs) in galactic nuclei via dynamical friction and two-body relaxation. Due to the high density, binaries in orbit around the SMBH can frequently undergo close encounters with compact remnants from the cusp. This can affect the gravitational wave merger rate of compact binaries in galactic nuclei. We investigated this process by means of high accuracy few-body simulations, performed with a novel Monte Carlo approach. We find that, around a SgrA*-like SMBH, three-body encounters increase the number of mergers by a factor of 3. This occurs because close encounters can reorient binaries with respect to their orbital plane around the SMBH, increasing the number of Kozai-Lidov induced mergers. We obtain a binary black hole merger rate of 1.6x10^-6/yr per Milky Way-like nucleus.

arXiv commentProceedings of the IAU symposium 351 (MODEST-19)

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• Compact Binary Coalescences: Astrophysical Processes and Lessons Learned
• Gravitational Waves from Hierarchical Triple Systems with Kozai-Lidov Oscillation
• Ready-to-use analytic model for gravitational waves from a hierarchical triple with Kozai-Lidov oscillations
• Tidal Disruption Events by Compact Supermassive Black Hole Binaries