High velocity stars from the interaction of a globular cluster and a massive black hole binary

TL;DR

This paper investigates how interactions between a globular cluster and a supermassive black hole binary can produce high velocity stars, some escaping the galaxy and others orbiting near the galactic center.

Contribution

It introduces a new mechanism for high velocity star production involving close interactions with a black hole binary in a galaxy.

Findings

Some stars gain enough velocity to escape the galaxy.

Stars are stripped from the globular cluster and orbit the galactic center.

Interaction can produce stars with velocities exceeding typical galactic escape speeds.

Abstract

High velocity stars are stars moving at velocities so high to require an acceleration mechanism involving binary systems or the presence of a massive central black hole. In the frame of a galaxy hosting a supermassive black hole binary (of total mass $10^8$ M$_\odot$), we investigated a mechanism for the production of high velocity stars due to the close interaction between a massive and orbitally decayed globular cluster and the super massive black hole binary. Some stars of the cluster acquire high velocities by conversion of gravitational energy into kinetic energy deriving from their interaction with the black hole binary. After the interaction, few stars reach a velocity sufficient to overcome the galactic gravitational well, while some of them are just stripped from the globular cluster and start orbiting around the galactic centre.