Are there Black Hole Symbiotic X-ray Binaries?

TL;DR

This study uses population synthesis and accretion modeling to explore the rarity of black hole symbiotic X-ray binaries in the Galaxy, finding they are significantly less common and less detectable than neutron star counterparts.

Contribution

The paper provides the first comprehensive simulation-based analysis of black hole symbiotic X-ray binaries, highlighting their scarcity and low detectability compared to neutron star systems.

Findings

BH SyXBs are at most one-sixth as numerous as NS SyXBs.

Less than 10% of BH SyXBs are detectable in X-ray.

The scarcity is influenced by supernova mechanisms, kick velocities, and wind properties.

Abstract

While there are over a dozen known neutron star (NS) symbiotic X-ray binaries (SyXBs) in the Galaxy, none SyXBs containing a black hole (BH) have been detected. We address this problem by incorporating binary population synthesis and the accretion properties of BHs fed by the wind from red giant companions. We investigate the impact of different supernova mechanisms, kick velocity distributions and wind velocities on the formation of both NS and BH SyXBs. Our simulations show that the number of BH SyXBs is at most one-sixth that of NS SyXBs in the Galaxy provided that the common envelope efficiency parameter $\alpha\sim 0.3-5$. And less than $\sim 10$ of BH SyXBs could be detectable in X-ray, considering their low radiation efficiencies. These findings indicate a scarcity of BH SyXBs in the Galaxy.