Simulations of Interacting Binary Systems -- Pathways to Radio Bright GRB Progenitors

Although the association of gamma-ray bursts (GRBs) with massive stellar death is on firm footing, the nature of the progenitor system and the key ingredients required for a massive star to produce a gamma-ray burst remain open questions. Here, we investigate the evolution of a massive star with a closely orbiting compact object companion using the stellar evolution code MESA. In particular, we examine how the companion influences the angular momentum and circumstellar environment near the end of the massive star life. We find that tidal effects can cause the compact object companion to significantly increase the angular momentum of the massive star, for orbital periods in the range of up to $\sim 4$ days. We model the density profile evolution of the massive star and discuss how tidal interactions may also lead to stripping of the outer stellar envelope in a way that can create an environment around the binary system that deviates from a typical $1/r^{2}$ wind density profile. We show how our results depend on the metallicity of the system, initial spin of the star, mass ratio, as well as accretion and dynamo prescriptions in the simulations. We conclude that these systems may be viable progenitors for radio-bright, long gamma-ray bursts.