High power accretion in massive binary systems and the impact of metallicity

Abstract

During a giant eruption of a very massive star in the binary system, the companion star can accrete a large amount of mass that can change its properties and potentially its subsequent evolution. The effect depends on the companion mass, metallicity, the amount of mass it accreted, orbital parameters and other parameters. We simulate individual companion stars assuming they undergo such accretion events. We study the envelope properties of 20 $M_{\odot }$ and 30 $M_{\odot }$ single massive stars at different metallicities ($Z=0.02$, $Z=0.008$ and $Z=0.004$) during accretion at different rates, from $10^{-5}$ to $10^{-2}{M}_{\odot }{\mathrm{yr}}^{-1}$. For the lower accretion rates we simulate, the stars remains hot, while at higher accretion rates, it becomes cooler and inflates. This behavior is observed in both stars but occurs at different accretion rates. Higher metallicity stars exhibit greater variations in accretion luminosity for the same accretion rate and stellar mass compared to lower metallicity stars. While higher metallicity stars typically have larger stellar envelopes, suggesting smaller variations in luminosity at Galactic metallicity compared to the LMC and SMC, our results show the opposite.