Be X-ray binaries consist of a NS and a rapidly rotating main-sequence star.
The NS accretes matter from the decretion disk, which surrounds the main-sequence star, and thus generates X-ray emission. We decided to study these systems with a synthetic population of massive stellar binaries evolved by the COMPAS code. Our preliminary results already hint to important conclusions on the efficiency of accretion during stable mass transfer and on the nature of the claimed bimodality in the NS spin period.
We expect these findings to affect predictions on the merger rate and mass distribution of double compact mergers.