Binary black hole growth by gas accretion in stellar clusters

TL;DR

This paper demonstrates that stellar-mass black hole binaries in young clusters can rapidly grow and harden through gas accretion, potentially explaining observed gravitational wave signals.

Contribution

It introduces a new model where black hole binaries grow significantly via gas accretion in protoglobular clusters, affecting their evolution and gravitational wave signatures.

Findings

Black holes can grow from 8 to 35 solar masses through accretion.

Gas accretion can lead to binary hardening before gas depletion.

This process offers a new formation channel for massive black hole binaries.

Abstract

We show that binaries of stellar-mass black holes formed inside a young protoglobular cluster, can grow rapidly inside the cluster's core by accretion of the intracluster gas, before the gas may be depleted from the core. A black hole with mass of the order of eight solar masses can grow to values of the order of thirty five solar masses in accordance with recent gravitational waves signals observed by LIGO. Due to the black hole mass increase, a binary may also harden. The growth of binary black holes in a dense protoglobular cluster through mass accretion indicates a potentially important formation and hardening channel.