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

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.