Contributed Talk - Splinter Stellar

Thursday, 24 September 2020, 14:05   (virtual room M)

Case A mass transfer: A comprehensive study of their observable stellar properties

Koushik Sen, Norbert Langer, Pablo Marchant, Selma de Mink, Laurent Mahy, Hughes Sana, Athira Menon
Argelander Institute for Astronomy

Massive binaries with initial orbital periods below ~10d undergo mass transfer via Roche-Lobe Overflow during core hydrogen burning (Case A). Rapid binary evolution models have not been able to produce reliable predictions for this stage. Here, we provide a comprehensive study of Case A binary evolution based on a dense grid of detailed models, resolving the initial parameter space with ~10000 individual calculations. We cover an initial primary mass range of 10-40 Msun and initial mass ratios from 0.275-0.975. Our models provide the duration of nuclear-timescale mass transfer as a function of initial parameters and the number of semi-detached binaries compared to non-interacting ones, as well as the expected general characteristics of semi-detached and of post-Case A mass transfer binaries (orbital period, stellar spins, mass ratio, surface abundances, etc.), assuming constant star formation. We compare our results with the comprehensive and unbiased VFTS-TMBM sample of massive binary stars in the 30 Doradus region, for which accurate orbital and stellar parameters have been derived (L. Mahy et al., 2020ab, A&A, in press). While we find generally good agreement, we obtain strong constraints on the Case A mass transfer efficiency for individual systems. We assess the importance of Case A mass transfer for producing massive X-ray binaries, double-compact object binaries, and different types of supernovae.