Modeling Supermassive Stellar Progenitors of Direct Collapse Black Hole Formation

Within a billion years of the Big Bang, young galaxies (and their central black holes) have grown from the coalescence and collapse of primordial stars. These galaxies are at the forefront of detection with the James Webb Space Telescope, while gravitational waves from the mergers of their central supermassive black holes (SMBHs) are key observational targets for the under-construction Laser Interferometer Space Antenna (LISA). The mechanism through which these SMBHs formed, however, is unclear. One proposal is the direct collapse of supermassive stars (SMSs); a process that could generate gravitational waves (GWs) detectable by LISA and other proposed detectors targeting the millihertz GW band. We employ initial conditions drawn from the Renaissance Simulations as input data to Modules for Experiments in Stellar Astrophysics (MESA), an open-source stellar evolution code, to evolve SMSs from the pre-main sequence through to the onset of the general-relativistic instability. We investigate the impact of stellar engineering choices on the eventual fate of these SMSs, present evolutionary tracks, and demonstrate that pre-collapse profiles can be passed to numerical relativity simulations for more accurate modeling of SMBH formation via direct collapse.