Importance of stable mass transfer and stellar winds for the formation of gravitational wave sources

Abstract

The large number of gravitational wave (GW) detections have revealed the properties of the merging black hole binary population, but their formation is still heavily debated. Understanding the imprint of stellar physics on the observable GW population will shed light on how we can use the gravitational wave data, along with other observations, to constrain the poorly understood evolution of massive binaries. We perform a parameter study for the classical isolated binary formation channel in order to better understand how sensitive the properties of the coalescing binary black hole population are on uncertainties related of stable mass transfer phase and stellar winds. We use the population synthesis code SeBa to simulate the evolution of massive binaries on a large range of metallicities. We vary five assumptions: 1 and 2) the mass transfer efficiency and the angular momentum loss during the first mass transfer phase, 3) the mass transfer stability criteria for giant donors with radiative envelopes, 4) the effective temperature at which an evolved star develops a deep convective envelope, and 5) the stellar winds. Our varied parameters have a complex, interrelated effects on the population properties of GW sources. Most notably, the impact of the mass transfer stability criteria parameter depends on the assumed mass transfer efficiency. The uncertainties in the assumed angular momentum loss have significant effects on the relative rates of the two dominant channels. Because of the numerous uncertainties and lack of reliable models direct inference of massive binary physics from gravitational data is not recommended.

From ZAMS to merger: Detailed binary evolution models of coalescing neutron star – black hole systems at solar metallicity

“…The primary reason for this is that the formulae do not track the mass of the developing He core of the main-sequence star and the radius evolution of the star used to infer the end of the mass transfer does not take into account altered structure of the stripped donor star. Both these factors can lead to more extended case-A mass-transfer cases, where a larger fraction of the donor star is transferred onto the accretor (see Dorozsmai & Toonen 2022, for an extended discussion).…”

On the Neutron Star/Black Hole Mass Gap and Black Hole Searches

“…Mass transfer stability in the binaries with an accreting BH and a massive donor has been frequently discussed over past years, since it was applied to understand the formation channel of binary BH mergers (e.g., Inayoshi et al 2017;Pavlovskii et al 2017;van den Heuvel et al 2017;Neijssel et al 2019;Shao & Li 2021b;Gallegos-Garcia et al 2021;Marchant et al 2021;Olejak et al 2021;Dorozsmai & Toonen 2022;van Son et al 2022). In some cases, mass-transferring BH binaries with a massive donor are likely to undergo the expansion or convection instability that followed by common-envelope evolution (Pavlovskii et al 2017).…”

Criteria for Dynamical Timescale Mass Transfer of Metal-poor Intermediate-mass Stars

“…Recent studies (Ge et al 2015;Pavlovskii et al 2017;Ge et al 2020a;Marchant et al 2021;Temmink et al 2023) suggest that the critical initial mass ratios for dynamical timescale mass transfer are larger than previously expected from polytropic stellar models, with the exception of massive early main-sequence (MS) stars (Ge et al 2015(Ge et al , 2020a. So, binaries in a stable mass-transfer channel contribute significantly to merging BHs (e.g., Inayoshi et al 2017;Gallegos-Garcia et al 2021;Briel et al 2022;Dorozsmai & Toonen 2022).…”