Analytic, dust-independent mass-loss rates for red supergiant winds initiated by turbulent pressure

TL;DR

This paper presents an analytic model showing that turbulent pressure alone can drive mass-loss in red supergiants, providing a dust-independent rate prescription that impacts stellar evolution understanding.

Contribution

It introduces the first fully analytic, dust-independent mass-loss rate model for red supergiants based on turbulent pressure effects.

Findings

Turbulent pressure explains observed mass-loss rates without dust opacity.

Provides a new analytic mass-loss rate prescription for red supergiants.

Suggests mass-loss rates may not depend directly on metallicity.

Abstract

Context. Red supergiants are observed to undergo vigorous mass-loss. However, to date, no theoretical model has succeeded in explaining the origins of these objects' winds. This strongly limits our understanding of red supergiant evolution and Type II-P and II-L supernova progenitor properties. Aims. We examine the role that vigorous atmospheric turbulence may play in initiating and determining the mass-loss rates of red supergiant stars. Methods. We analytically and numerically solve the equations of conservation of mass and momentum, which we later couple to an atmospheric temperature structure, to obtain theoretically motivated mass-loss rates. We then compare these to state-of-the-art empirical mass-loss rate scaling formulae as well as observationally inferred mass-loss rates of red supergiants. Results. We find that the pressure due to the characteristic turbulent velocities inferred for red supergiants is sufficient to explain the mass-loss rates of these objects in the absence of the normally employed opacity from circumstellar dust. Motivated by this initial success, we provide a first theoretical and fully analytic mass-loss rate prescription for red supergiants. We conclude by highlighting some intriguing possible implications of these rates for future studies of stellar evolution, especially in light of the lack of a direct dependence on metallicity.