Constraining accretion efficiency in massive binary stars with LIGO -Virgo black holes

The growing sample of LIGO–Virgo black holes (BHs) opens new perspectives for the study of massive binary evolution. Here, we study the impact of mass accretion efficiency and common envelope on the properties of binary BH (BBH) mergers, by means of population synthesis simulations. We model mass accretion efficiency with the parameter fMT ∈ [0.05, 1], which represents the fraction of mass lost from the donor which is effectively accreted by the companion. Lower values of fMT result in lower BBH merger rate densities and produce mass spectra skewed towards lower BH masses. Our hierarchical Bayesian analysis, applied to BBH mergers in the first and second gravitational-wave transient catalogue, yields zero support for values of fMT ≲ 0.6, with a lower boundary of the 99 per cent credible intervals equal to fMT = 0.59. This result holds for all the values of the common-envelope efficiency parameter we considered in this study αCE ∈ [1, 10]. This confirms that gravitational-wave data can be used to put constraints on several uncertain binary evolution processes.