Evolutionary models have shown the substantial effect that strong mass-loss rates (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 M -luminosity relations to calculate evolution. Empirical prescriptions usually scale with luminosity and effective temperature, but M should also depend on the current mass and hence the surface gravity of the star, yielding more than one possible M for the same position on the Hertzsprung-Russell diagram. One can solve this degeneracy by measuring M for RSGs that reside in clusters, where age and initial mass (Minit) are known. In this paper we derive M 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 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.
Bibliographical noteFunding Information:
We would like to thank the anonymous referee for useful comments which helped improve the paper. Based in part on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NNA17BF53C, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. Financial support for this work was provided by NASA through award # 05 0064 issued by USRA. Support for this work was provided by NASA through Hubble Fellowship grant HST-HF2-51428 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. RDG was supported by NASA and the United States Air Force.
© 2020 The Author(s)
- Galaxies: clusters: individual
- Stars: evolution
- Stars: mass-loss
- Stars: massive