Adiabatic Mass Loss in Binary Stars. V. Effects of Metallicity and Nonconservative Mass Transfer -- Application in High Mass X-ray Binaries

TL;DR

This paper investigates how metallicity and nonconservative mass transfer influence the stability of mass transfer in binary stars, with implications for high-mass X-ray binaries and other astrophysical phenomena.

Contribution

It provides a systematic survey of critical mass ratios considering metallicity and nonconservative effects, enhancing understanding of binary star evolution.

Findings

Metal-poor radiative-envelope donors have smaller critical mass ratios than solar-metallicity stars.

Nonconservative mass transfer reduces critical mass ratios for massive donors.

Theoretical predictions align well with observed high-mass X-ray binary mass ratios.

Abstract

Binary stars are responsible for many unusual astrophysical phenomena, including some important explosive cosmic events. The stability criteria for rapid mass transfer and common-envelope evolution are fundamental to binary star evolution. They determine the mass, mass ratio, and orbital distribution of systems such as X-ray binaries and merging gravitational-wave sources. We use our adiabatic mass-loss model to systematically survey metal-poor and solar-metallicity donor thresholds for dynamical timescale mass transfer. The critical mass ratios qad are systematically explored, and the impact of metallicity and nonconservative mass transfer are studied. For metal-poor radiative-envelope donors, qad are smaller than those for solar-metallicity stars at the same evolutionary stage. However, qad do the opposite for convective-envelope donors. Nonconservative mass transfer significantly decreases qad for massive donors. This is because it matters how conservative mass transfer is during the thermal timescale phase immediately preceding a delayed dynamical mass transfer. We apply our theoretical predictions to observed high-mass X-ray binaries that have overfilled their Roche lobes and find a good agreement with their mass ratios. Our results can be applied to study individual binary objects or large samples of binary objects with binary population synthesis codes.