A new mass-loss rate prescription for red supergiants. Issue 4 (5th February 2020)

• Record Type: Journal Article
• Authors: Beasor, Emma R; Davies, Ben; Smith, Nathan; van Loon, Jacco Th; Gehrz, Robert D; Figer, Donald F
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 492:Issue 4(2020)
• Page Start: 5994
• Page End: 6006
• Publication Date: 2020-02-05
• Subjects: stars: evolution -- stars: massive -- stars: mass-loss -- supergiants -- galaxies: clusters: individual; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa255
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Evolutionary models have shown the substantial effect that strong mass-loss rates ($\dot{M}$ s) can have on the fate of massive stars. Red supergiant (RSG) mass-loss is poorly understood theoretically, and so stellar models rely on purely empirical $\dot{M}$ –luminosity relations to calculate evolution. Empirical prescriptions usually scale with luminosity and effective temperature, but $\dot{M}$ should also depend on the current mass and hence the surface gravity of the star, yielding more than one possible $\dot{M}$ for the same position on the Hertzsprung–Russell diagram. One can solve this degeneracy by measuring $\dot{M}$ for RSGs that reside in clusters, where age and initial mass ( M init ) are known. In this paper we derive $\dot{M}$ values and luminosities for RSGs in two clusters, NGC 2004 and RSGC1. Using newly derived M init measurements, we combine the results with those of clusters with a range of ages and derive an M init -dependent $\dot{M}$ prescription. When comparing this new prescription to the treatment of mass-loss currently implemented in evolutionary models, we find models drastically overpredict the total mass-loss, by up to a factor of 20. Importantly, the most massive RSGs experience the largest downward revision in their mass-loss rates, drastically changing the impact of wind mass-loss on their evolution. Our results suggest that for most initial masses of RSG progenitors, quiescent mass-loss during the RSG phase is not effective at removing a significant fraction of the H-envelope prior to core-collapse, and we discuss the implications of this for stellar evolution and observations of SNe and SN progenitors.