A new mass-loss rate prescription for red supergiants

Beasor, Emma R.; Davies, Ben; Smith, Nathan; Van Loon, Jacco Th; Gehrz, Robert D.; Figer, Donald F.

Abstract

Evolutionary models have shown the substantial effect that strong mass-loss rates ($\dotM$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 $\dotM$–luminosity relations to calculate evolution. Empirical prescriptions usually scale with luminosity and effective temperature, but $\dotM$ should also depend on the current mass and hence the surface gravity of the star, yielding more than one possible $\dotM$ for the same position on the Hertzsprung–Russell diagram. One can solve this degeneracy by measuring $\dotM$ for RSGs that reside in clusters, where age and initial mass (Minit) are known. In this paper we derive $\dotM$ values and luminosities for RSGs in two clusters, NGC 2004 and RSGC1. Using newly derived Minit measurements, we combine the results with those of clusters with a range of ages and derive an Minit-dependent $\dotM$ 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.

Citation

Beasor, E. R., Davies, B., Smith, N., Van Loon, J. T., Gehrz, R. D., & Figer, D. F. (2020). A new mass-loss rate prescription for red supergiants. Monthly Notices of the Royal Astronomical Society, 492(4), 5994 - 6006. https://doi.org/10.1093/mnras/staa255

• Journal Article Type: Article
• Acceptance Date: Jan 19, 2020
• Online Publication Date: Feb 5, 2020
• Publication Date: 2020-03
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 492
• Issue: 4
• Pages: 5994 - 6006
• DOI: https://doi.org/10.1093/mnras/staa255
• Keywords: stars: evolution; stars: massive; stars: mass-loss; supergiants; galaxies: clusters: individual
• Publisher URL: https://doi.org/10.1093/mnras/staa255