A Model for Eruptive Mass Loss in Massive Stars

TL;DR

This paper introduces a 1D stellar evolution model that explains eruptive mass loss in massive stars via super-Eddington luminosities, impacting their evolution and observed supergiant populations.

Contribution

The paper presents a novel 1D model for eruptive mass loss driven by super-Eddington luminosities, implemented in MESA, and explores its effects on massive star evolution.

Findings

Eruptive mass loss rates up to 0.01 solar masses per year.

Mass loss occurs in a specific temperature band on the HR diagram.

Prevents stars >20 solar masses from becoming red supergiants.

Abstract

Eruptive mass loss in massive stars is known to occur, but the mechanism(s) are not yet well-understood. One proposed physical explanation appeals to opacity-driven super-Eddington luminosities in stellar envelopes. Here, we present a 1D model for eruptive mass loss and implement this model in the MESA stellar evolution code. The model identifies regions in the star where the energy associated with a locally super-Eddington luminosity exceeds the binding energy of the overlaying envelope. The material above such regions is ejected from the star. Stars with masses $10-100~M_\odot$ at solar and SMC metallicities are evolved through core helium burning, with and without this new eruptive mass-loss scheme. We find that eruptive mass loss of up to $\sim10^{-2}~M_\odot \mathrm{yr}^{-1}$ can be driven by this mechanism, and occurs in a vertical band on the HR diagram between $3.5 \lesssim \log(T_\mathrm{eff}/\mathrm{K}) \lesssim 4.0$. This predicted eruptive mass loss prevents stars of initial masses $\gtrsim20~M_\odot$ from evolving to become red supergiants, with the stars instead ending their lives as blue supergiants, and therefore offers a possible explanation for the observed lack of red supergiants in that mass regime.