The role of natal kicks in forming asymmetric compact binary mergers

Understand

In their most recent observing run, the LIGO-Virgo-KAGRA (LVK) Collaboration observed gravitational waves (GWs) from compact binary mergers with highly asymmetric mass ratios, including both binary black holes (BBHs) and neutron star--black holes (NSBHs).

• It appears that NSBHs with mass ratios $q\simeq0.2$ are more common than equally asymmetric BBHs, but the reason for this remains unclear.
• We use the binary population synthesis code COSMIC to investigate the evolutionary pathways leading to the formation and merger of asymmetric compact binaries.
• We find that within the context of isolated binary stellar evolution, most asymmetric mergers start off as asymmetric stellar binaries.