Be X-ray binaries in the Small Magellanic Cloud: A hint of the accretion efficiency during mass transfer?

Wed 27th Nov 2019 @2:15 PM, level 7 Conference Room, David Caro Building
Dr Serena Vinciguerra Max Planck Institute for Gravitational Physics



Be X-ray binaries (BeXBs) consist of rapidly rotating Be stars with neutron star companions accreting from the emission disk. We compare the observed population of BeXBs in the Small Magellanic Cloud to simulated populations of BeXB-like systems produced with the COMPAS population synthesis code. We focus on the apparently higher minimal mass of Be stars in BeXBs than in the Be population at large. Assuming that BeXBs experienced only dynamical stable mass transfer, their mass distribution suggests that the efficiency of accretion rarely drops below ~30%. We also investigate the observed orbital period distribution and number of observed systems, looking for further constraints on our mass transfer models. Finally, we argue if ultra stripped stars could lead to fast rotating neutron stars in BeXBs. We expect our findings to affect our previous predictions on the population of double compact mergers.