Gamma Ray Bursts from Black Hole - Star Collisions in Globular Clusters

Posted: Wednesday, August 22, 2018
Last Updated: August 22, 2018

In dense stellar environments such as globular clusters (GCs), close passages during dynamical interactions can lead to tidal disruptions or even physical collisions between stars. In this analysis, we use our Cluster Monte Carlo computer code to study collisions between BHs and stars in GCs. One of the most impactful initial parameters for a GC is the initial virial radius.. The virial radius determines the cluster density which, in turn, determines the collision rate. A smaller initial virial radius, which corresponds to a higher stellar density, results in earlier collisions compared to the systems with a larger initial virial radius. We perform cosmological rate calculations to estimate the rate of collisions between BHs and stars in a typical GC. Collisions of this type may connect to events that resemble gamma ray bursts. We estimate a collision rate of 15.4 Gpc-3 yr-1 for high-mass collisions out to a redshift of 3.5. For low-mass collisions, we estimate a rate of 30.2 Gpc-3 yr-1 within the same redshift. Within the uncertainties of this analysis, these rates are roughly consistent with the observed GRB rate.

For more information on this topic, there should be a paper published in a few months from when this was originally posted. The link will be shared here when it is complete. There is also a poster on this topic that will be presented at the AAS Meeting in the winter of 2019. The poster is seen below.