Binary Disruption by Massive Black Holes: Hypervelocity Stars, S Stars, and Tidal Disruption Events

TL;DR

This paper investigates how the tidal disruption of binary stars by massive black holes can lead to the formation of hypervelocity stars and contribute significantly to black hole growth over cosmic timescales.

Contribution

It introduces a model linking binary disruption to black hole growth and explains the observed rates of hypervelocity stars and S stars in the Milky Way.

Findings

Disrupted binaries produce hypervelocity stars and bound companions at rates of 10^{-5}--10^{-3} per year.

The disruption process can fuel black hole growth comparable to other accretion mechanisms.

Rates are consistent with observations in the Milky Way and nearby galaxies.

Abstract

We examine whether disrupted binary stars can fuel black hole growth. In this mechanism, tidal disruption produces a single hypervelocity star (HVS) ejected at high velocity and a former companion star bound to the black hole. After a cluster of bound stars forms, orbital diffusion allows the black hole to accrete stars by tidal disruption at a rate comparable to the capture rate. In the Milky Way, HVSs and the S star cluster imply similar rates of 10^{-5}--10^{-3} yr^{-1} for binary disruption. These rates are consistent with estimates for the tidal disruption rate in nearby galaxies and imply significant black hole growth from disrupted binaries on 10 Gyr time scales.