Black Holes in Dense Star Clusters

Most stars form in dense clusters, the largest of which can contain up to many millions of them. Stars in these clusters are born with a broad mass spectrum and the most massive ones evolve quickly, ending their lives in as little as a few million years and leaving behind black holes or neutron stars as remnants. The star clusters themselves, however, can continue to live for many billions of years, and indeed the globular clusters seen in all galaxies are thought to contain some of the oldest stars in the Universe. Therefore, many of the star clusters observed today can contain large numbers of black holes and neutron stars formed a long time ago. This work will use state-of-the-art supercomputer simulations to study the formation and evolution of these compact objects in a variety of star cluster environments. The main focus will be on the production of tight binaries containing two black holes, which can eventually merge and produce potentially detectable bursts of gravitational radiation. Additionally, binaries in which a black hole or neutron star accretes from an ordinary stellar companion will also be studied; these can become bright X-ray sources and produce rapidly spinning pulsars.