On the Formation of Galactic Black Hole Low-Mass X-ray Binaries

TL;DR

This paper investigates the formation of galactic black hole low-mass X-ray binaries using stellar evolution and binary population synthesis, providing insights into their evolutionary history and the impact of supernova mechanisms.

Contribution

It offers a comprehensive analysis of BH LMXB formation, testing various assumptions and constraining key parameters with observational data.

Findings

BH LMXBs can form via standard CE scenario with failed supernovae.

Constraints on supernova mechanisms and binary parameters.

Predicted distributions of donor mass, temperature, and orbital period.

Abstract

Currently, there are 24 black hole (BH) X-ray binary systems that have been dynamically confirmed in the Galaxy. Most of them are low-mass X-ray binaries (LMXBs) comprised of a stellar-mass BH and a low-mass donor star. Although the formation of these systems has been extensively investigated, some crucial issues remain unresolved. The most noticeable one is that, the low-mass companion has difficulties in ejecting the tightly bound envelope of the massive primary during the spiral-in process. While initially intermediate-mass binaries are more likely to survive the common envelope (CE) evolution, the resultant BH LMXBs mismatch the observations. In this paper, we use both stellar evolution and binary population synthesis to study the evolutionary history of BH LMXBs. 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 constraints on the aforementioned parameters. 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.