Constraints on the contributions to the observed binary black hole population from individual evolutionary pathways in isolated binary evolution

Abstract

Gravitational waves from merging binary black holes can be used to shed light on poorly understood aspects of massive binary stellar evolution, such as the evolution of massive stars (including their mass-loss rates), the common envelope phase, and the rate at which massive stars form throughout the cosmic history of the Universe. In this paper we explore the correlated impact of these phases on predictions for the merger rate and chirp mass distribution of merging binary black holes, aiming to identify possible degeneracies between model parameters. In many of our models, a large fraction (more than 70 per cent of detectable binary black holes) arise from the chemically homogeneous evolution scenario; these models tend to over-predict the binary black hole merger rate and produce systems which are on average too massive. Our preferred models favour enhanced mass-loss rates for helium rich Wolf–Rayet stars, in tension with recent theoretical and observational developments. We identify correlations between the impact of the mass-loss rates of Wolf–Rayet stars and the metallicity evolution of the Universe on the rates and properties of merging binary black holes. Based on the observed mass distribution, we argue that the $\sim 10{{\%}}$ of binary black holes with chirp masses greater than 40 M⊙ (the maximum predicted by our models) are unlikely to have formed through isolated binary evolution, implying a significant contribution (>10 per cent) from other formation channels such as dense star clusters or active galactic nuclei. Our models will enable inference on the uncertain parameters governing binary evolution in the near future.

LIGO–Virgo–KAGRA's Oldest Black Holes: Probing Star Formation at Cosmic Noon With GWTC-3

“…In reality, the observed population of merging BBHs is most likely a mixture of multiple formation channels with a corresponding mixture of delay time distributions (e.g., Bouffanais et al 2021;Zevin et al 2021;Stevenson & Clarke 2022;Godfrey et al 2023). Future work should simultaneously incorporate delay time distributions from several formation channels, including predictions from nonisolated binary evolution channels.…”

Precision cosmology with primordial GW backgrounds in presence of astrophysical foregrounds

“…These fractions cannot be discriminated from e at merging, given that the orbits have already circularised, but from the study of mass, spin and redshift distributions and the comparison with simulated catalogues. Future data and developments of semi-analytical modelling of BBH-forming environments will allow to refine these analyses, and a growing body of studies in the literature (with very few exceptions [89]) finds that a fraction O(0.1 − 1) of the BBHs measured by LVK is of dynamical origin [90][91][92][93][94][95].…”

Stellar Properties of Observed Stars Stripped in Binaries in the Magellanic Clouds

“…For future evolution, the stripped star winds directly affect the amount of hydrogen leftover from interaction and thus the supernova type (Gilkis et al 2019). They also determine the orbital widening of short-period stripped star + compact object binaries and therefore also their ability to merge in gravitational-wave events (Broekgaarden et al 2022;Stevenson & Clarke 2022).…”