Formation of binaries of solar-type stars with a black hole companion

After the discovery of gravitational waves (GWs, Abbott et al. 2016), the LIGO-Virgo gravitational wave (GW) interferometers have detected 90 compact object coalescences of which the vast majority are binary black holes (BBH). A popular scenario for their origin is that these BBH form in dynamical interactions in dense stellar systems, such as globular clusters (GCs, e.g. Antonini et al. 2023). 

 

To understand the importance of this `dynamical channel' it is critical to know how ubiquitous black holes (BHs) are in GCs. Several BH candidates have been found, of which the discovery of solar-type stars with a BH companion are the most convincing (Giesers et al. 2018). These systems are unlikely to have formed like this, because it would imply an extreme mass ratio at formation. A more likely formation channel is that these binaries formed in an exchange interaction between a binary star and a BH (Kremer et al. 2018), which are common in GCs. 

 

To understand this process better, you will run gravitational "scattering experiments" of binary - binary and binary - single interactions, to quantify the cross sections for exchange and to determine the rates of formation of binaries with a solar-type star and a black hole. You will then make assumptions for the binary distribution of stars and BHs and determine the new distributions after interactions have taken place. This study will make useful predictions for ongoing observational surveys of GCs that aim to detect BHs in binary systems through radial velocity variations.