Calibrating Eruptive Mass Loss in Red Supergiants with Local Group Data

TL;DR

This paper calibrates a super-Eddington eruptive mass-loss model for red supergiants using Local Group data, revealing a metallicity-dependent trend that influences stellar evolution and supernova progenitors.

Contribution

It introduces a calibrated, physically motivated eruptive mass-loss prescription for RSGs based on Local Group stellar populations and models its impact across different metallicities.

Findings

Eruptive mass loss strength increases with metallicity.

Calibrated parameters: ξ_SMC=0.0-0.05, ξ_LMC=0.1, ξ_M31=0.35.

Eruptive mass loss prevents stars >20 M_sun from becoming RSGs.

Abstract

We calibrate a physically motivated, super-Eddington eruptive mass-loss prescription for red supergiants (RSGs) using Local Group stellar populations. Building on MESA models that add eruptive mass loss with a free scaling parameter $\xi$, we generate stellar evolution tracks and isochrones, and synthesize mock populations at metallicities of $Z/Z_\odot=0.2,\ 0.4$, and $1.0$. We compare model luminosity functions to observations of RSGs in the SMC, LMC, and M31, restricting to $3.5<\log T_{\rm eff}/K<3.75$ and $\log(L/L_\odot)>4.5$. By-eye fits to the observations yield values of $\xi_\mathrm{SMC}=0.0-0.05$, $\xi_\mathrm{LMC}=0.1$, and $\xi_\mathrm{M31}=0.35$, implying a positive, linear trend between the strength of eruptive mass-loss and metallicity. This calibrated eruptive mass loss prevents stars with initial masses $\gtrsim 20~M_\odot$ from evolving to become red supergiants, with implications for the mass spectrum of core-collapse progenitors, compact remnants, early supernova interaction signatures, and the spectral energy distributions of unresolved galaxies.