January 2024
Speaker: Kyle Akira Rocha
Title: To Be or not to Be: the role of rotation in modeling Galactic Be X-ray binaries
Abstract: X-ray binaries (XBRs) are testbeds for modeling binary and stellar evolution. Be-XRBs are the most numerous subclass of observed high-mass XRBs, containing Be donors with neutron star (NS) and black hole (BH) companions. While the exact mechanism responsible for the Be phenomenon remains under debate, stellar rotation has been identified as a key ingredient for the formation of the decretion disk. Previous population synthesis studies have used the Be-XRB population to constrain binary evolution processes such as mass transfer and common envelope efficiency, but without self-consistent rotational modeling. We use POSYDON, a next generation population synthesis code coupled with binary MESA models, to explore the binary formation scenario for Be-XRBs. We explicitly model the rotational evolution of both stars during mass transfer and investigate the implications on selecting Be-XRB like systems. We successfully reproduce broad features of the orbital distribution of observed Be-XRBs and find a donor rotational distribution consistent with recent literature. Our results demonstrate the necessity of accurately modeling stellar rotation to interpret the Be-XRB population.