The effect of mass loss in models of red supergiants in the Small Magellanic Cloud

TL;DR

This study investigates how different mass-loss prescriptions affect the evolution and observable properties of red supergiants in the Small Magellanic Cloud, revealing inconsistencies with observations and emphasizing uncertainties in modeling stellar mass loss.

Contribution

It compares various recent mass-loss prescriptions for RSGs, analyzing their impact on stellar evolution and observational constraints, and highlights the need for improved models.

Findings

Higher mass-loss rates lead to earlier envelope stripping and shorter RSG lifetimes.

None of the prescriptions fully match all observational data.

Increased mass loss improves the luminosity function agreement but predicts undetected luminous progenitors.

Abstract

The rate and mechanism of mass loss of red supergiants (RSGs) remain poorly understood, especially at low metallicities. Motivated by the new empirical prescription by Yang et al. 2023, based on the largest and most complete sample in the Small Magellanic Cloud, we investigate the impact of different popular and recent RSG mass-loss prescriptions that span a range of RSG mass-loss rates on the evolution and observable properties of single massive stars. Our results show that higher mass-loss rates result in earlier envelope stripping and shorter RSG lifetimes, particularly for the more luminous stars, leading to a steeper luminosity function and predicting hotter final positions for the SN progenitors. None of the considered mass-loss prescriptions is fully consistent with all observational constraints, highlighting ongoing uncertainties in deriving and modeling RSGs mass loss. The mass-loss rates suggested by Kee et al. predict rapid envelope stripping, inconsistent with the observed population of luminous RSGs and SN progenitor detections, while the models implementing the commonly used de Jager et al. and the recent Beasor et al. prescriptions overestimate the number of luminous RSGs. While the increased mass-loss rates for luminous RSGs predicted by Yang et al. lead to better agreement with the observed RSG luminosity function, naturally reproducing the updated Humphreys-Davidson limit, they also produce luminous yellow supergiant progenitors not detected in nearby supernovae. We also estimate that binary interactions tend to slightly increase the formation of luminous RSGs due to mass accretion or merging. Our study examines the impact of RSG mass loss during the late stages of massive stars, highlighting the significance of using comprehensive observational data, exploring the uncertainties involved, and considering the effects of binary-induced or episodic mass loss.