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

TL;DR

This paper investigates the stability criteria for rapid mass transfer in metal-poor intermediate-mass stars, providing critical mass ratio thresholds and applying these to predict X-ray luminosity ranges in intermediate-mass X-ray binaries.

Contribution

The study offers new adiabatic mass-loss models and fitting formulas for critical mass ratios, incorporating metallicity effects, to improve understanding of binary star evolution.

Findings

Critical mass ratios are provided for $Z=0.001$ and $Z=0.02$.

Predicted upper limits to mass ratios match observed IMXBs.

Range of X-ray luminosities for IMXBs is estimated based on donor mass.

Abstract

The stability criteria of rapid mass transfer and common envelope evolution are fundamental in binary star evolution. They determine the mass, mass ratio and orbital distribution of many important systems, such as X-ray binaries, Type Ia supernovae and merging gravitational wave sources. We use our adiabatic mass-loss model to systematically survey the intermediate-mass stars' thresholds for dynamical-timescale mass transfer. The impact of metallicity on the stellar responses and critical mass ratios is explored. Both tables ($Z=0.001$) and fitting formula ($Z=0.001$ and $Z=0.02$) of critical mass ratios of intermediate-mass stars are provided. An application of our results to intermediate-mass X-ray binaries (IMXBs) is discussed. We find that the predicted upper limit to mass ratios, as a function of orbital period, is consistent with the observed IMXBs that undergo thermal or nuclear timescale mass transfer. According to the observed peak X-ray luminosity $L_\mathrm{X}$, we predict the range of $L_\mathrm{X}$ for IMXBs as a function of the donor mass and the mass transfer timescale.