On the formation of galactic black hole low-mass X-ray binaries

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.

Dynamical formation of black hole low-mass X-ray binaries in the field: an alternative to the common envelope

“…We wish to mention that the observed CMF is in tension with the results of population synthesis of LMXBs through CE evolution for various CE energy binding parameters proposed up to date (Wiktorowicz et al 2014), as they generally result in a distribution peaking strongly around 1.0 M ⊙ with a possible smaller peak around 0.2-0.3 M ⊙ . Similar results were obtained by Wang et al (2016), although it seems that a better agreement with observations could potentially be obtained if BH were formed in failed SN (Kochanek 2014) rather than through material fallback ). In the meantime channels involving intermediate mass donors (Justham et al 2006;Chen & Li 2006) are also inconsistent with observations as they predict donor spectral types which are too hot to explain the observed temperatures of companion stars in BH LMXBs.…”

“…In an attempt to justify such increased efficiency several modified CE models were proposed (see Li 2015 and references therein). Population synthesis studies have recently shown, however, that CE models in their current state fail to reproduce the distribution of donor mass of the observed BH LMXBs (Wiktorowicz et al 2014;Wang et al 2016), implying the need for either a more significant adjustment of the CE modeling or an alternative formation scenario to be considered.…”

Formation and Evolution of Compact Object Binaries in AGN Disks

“…Although these binaries may hide the cutoff at ∼ 1 pc, the fraction of the pre-existing binaries in galactic nuclei is poorly constrained. Due to rapid hardening expected during the common envelope phase, the formation of LMXBs is puzzling (Podsiadlowski et al 2003;Wiktorowicz et al 2014;Li 2015;Wang et al 2016). This is especially the case in galactic nuclei where only hard binaries are long-lived, so that surviving the common envelope phase without merging is even more difficult (Stephan et al 2019).…”

Low-mass X-ray binaries from black hole retaining globular clusters

“…This observation coupled with an estimate for the fraction of the BH population expected to be in accreting bina-Email: mgiesler@tapir.caltech.edu ries (Ivanova et al 2010) suggests that M22 may contain between 5 − 100 BHs (Strader et al 2012). Recent theoretical studies, including some detailed N-body simulations (e.g., Aarseth 2012; Wang et al 2016), support the idea that GCs are capable of retaining from a few to hundreds of BHs (e.g., Breen & Heggie 2013;Morscher et al 2013;Sippel & Hurley 2013;Rodriguez et al 2016b).…”