Ultra-compact X-ray binaries in the Galactic Bulge

Abstract

We model the present-day number and characteristics of Ultra-compact X-ray binaries (UCXBs) in the Galactic Bulge. The main objective is to compare the results with the forthcoming data from the Galactic Bulge Survey (GBS) in order to learn about formation scenarios, notably core collapse supernova rate, common envelope evolution and dynamical interactions, as well as the binary initial mass function. We use a binary population synthesis code and detailed stellar evolutionary tracks, combined with observations of the 11 known UCXBs. We predict a few hundred faint UCXBs with periods of 20-40 minutes that would be detectable by the GBS.