Binary Population Synthesis: Low- and Intermediate-Mass X-Ray Binaries

As has only recently been recognized, X-ray binaries with intermediate-mass secondaries are much more important than previously believed. To assess the relative importance of low- and intermediate-mass X-ray binaries (LMXBs and IMXBs), we have initiated a systematic study of these systems consisting of two parts: an exploration of the evolution of LMXBs and IMXBs for a wide range of initial masses and orbital periods using detailed binary stellar evolution calculations, and an integration of these results into a Monte-Carlo binary population synthesis code. Here we present some of the main results of our binary calculations and some preliminary results of the population synthesis study for a standard'' reference model. While the inclusion of IMXBs improves the agreement with the observed properties of LMXBs’', several significant discrepancies remain, which suggests that additional physical processes need to be included in the model.