Compact Binaries in Star Clusters I - Black Hole Binaries Inside Globular Clusters

TL;DR

This study models black hole binaries in star clusters, revealing their formation, interactions, and potential as sources for gravitational wave detectors, emphasizing the importance of clusters in binary population predictions.

Contribution

It provides a self-consistent simulation of black hole binary dynamics in star clusters, highlighting their formation, destruction, and potential as gravitational wave sources.

Findings

Black holes become centrally concentrated due to mass segregation.

Black hole-black hole binaries form efficiently but are often ejected or destroyed.

Potential LISA sources include highly eccentric black hole binaries.

Abstract

We study the compact binary population in star clusters, focusing on binaries containing black holes, using a self-consistent Monte Carlo treatment of dynamics and full stellar evolution. We find that the black holes experience strong mass segregation and become centrally concentrated. In the core the black holes interact strongly with each other and black hole-black hole binaries are formed very efficiently. The strong interactions, however, also destroy or eject the black hole-black hole binaries. We find no black hole-black hole mergers within our simulations but produce many hard escapers that will merge in the galactic field within a Hubble time. We also find several highly eccentric black hole-black hole binaries that are potential LISA sources, suggesting that star clusters are interesting targets for space-based detectors. We conclude that star clusters must be taken into account when predicting compact binary population statistics.