A Model for Eruptive Mass Loss in Massive Stars

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_ 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 ~10⁻²~M_ yr⁻¹ can be driven by this mechanism, and occurs in a vertical band on the HR diagram between 3.5 log(Tₑff/K) 4.0. This predicted eruptive mass loss prevents stars of initial masses 20~M_ 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.