The treasure of Be X-ray binaries in the Small Magellanic Cloud

Thursday, December 3, 2020 -
4:00pm to 5:00pm
Phillips Auditorium (Virtual)
University of Amsterdam

Be X-ray binaries (BeXRBs) consist of rapidly rotating Be stars with neutron star companions accreting from the circumstellar decretion disk of the Be star. We compare the observed population of BeXRBs in the Small Magellanic Cloud (SMC) with simulated populations of BeXRB-like systems produced with the COMPAS population synthesis code. We try to explain why Be stars in BeXRBs seem to not populate the same low mass range observed in the general population of Be stars. Assuming that BeXRBs experienced only stable mass transfer, their mass distribution suggests that at least ∼ 30% of the mass donated by the progenitor of the neutron star is typically accreted by the B-star companion. We expect these results to affect predictions for the population of double compact object mergers. Our convolution of the simulated BeXRB population with the star formation history of the SMC also reveals that the excess of BeXRBs is most likely explained by this galaxy’s burst of star formation ∼20–40 Myr ago, although the small metallicity of the SMC may have a considerable impact on the longevity of these systems.

The constraints posed by this population of BeXRBs on mass transfer accretion and the importance of star formation rate are the two main results we focused on in our first investigation; however we are not yet at the bottom of this BeXRB treasure chest…

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