Analytic, Turbulent Pressure Driven Mass Loss Rates from Red Supergiants

Abstract

AbstractAlthough red supergiants (RSGs) are observed to be undergoing vigorous mass loss, explaining the mechanism launching their winds has been a long-standing problem. Given the importance of mass loss to stellar evolution in this phase, this is a key uncertainty. In this contribution we present a recently published model (Kee et al. 2021) showing that turbulent pressure alone can extend the stellar atmosphere of an RSG to the degree that a wind is launched. This provides a fully analytic mass-loss prescription for RSGs. Moreover, utilising observationally inferred turbulent velocities for these objects, we find that this wind can carry an appropriate amount of mass to overall match observations. Intriguingly, when coupled to stellar evolution models the predicted mass-loss rates show that stars with initial masses above Mini∼17M⊙ may naturally evolve back to the blue and as such not end their lives as RSGs; this is also in overall good agreement with observations, here of Type II-P/L supernova progenitors. Moreover, since the proposed wind launching mechanism is not necessarily sensitive to metallicity, this could have important implications for stellar evolution predictions in low-metallicity environments.