On The Formation Of Galactic Black Hole Low-Mass X-ray Binaries

Currently, there are 24 black hole X-ray binary systems (BH XRB) that have been dynamically confirmed in the Galaxy. Most of them are low-mass X-ray bina-ries (LXMBs) comprised of a stellar-mass BH and a low-mass donor star. Although the formation of these systems has been extensively investigated, it is very hard to re-produce such systems with population synthesis studies. The most noticeable problem is that, the low-mass companion has difficulties in ejecting the tightly bound envelope of the massive primary during the common envelope (CE) evolution. While initially intermediate-mass binaries are more likely to survive the CE phase, the resultant BH LMXBs mismatch the observations. In this paper, we use both stellar evolution code and binary population synthesis to study the evolutionary history of BH LMXBs.In Chapter 1, we briefly introduce the observation features and the formation and evolution of LMXBs. In Chapter 2, we investigate the binding energy parameter λ for CE evolution. In previous work, it has been erroneously adopted as a constant in most of the population synthesis calculations. However, it is well known that λ varies during the stellar evolution. We use the updated MESA code to systematically calculate the values of λ for stars of masses 1-60 M☉. We adopt the criterion for the core-envelope boundary to be the maximum compression point in the hydrogen burning shell. We also investigate a new kind of λ with the enthalpy prescription. At last, we present fitting formulae for the calculated λ, which can be used in the future population synthesis studies.In Chapter 3, we test various assumptions and prescriptions for the supernova mechanisms that produce BHs, the binding energy parameter, the CE efficiency, and the initial mass distributions of the companion stars. We obtain the birthrate and the distributions of the donor mass, effective temperature and orbital period for the BH LMXBs in each case. By Comparing the calculated results with the observations, we put useful constrains on the aforementioned paramters. In particular, we show that it is possible to form BH LMXBs with the standard CE scenario if most BHs are born through failed supernovae.