Calibrating Eruptive Mass Loss in Red Supergiants with Local Group Data

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 $Z\mathrm{/}{Z}_{\odot }=0.2,0.4$, and $1.0$. We compare model luminosity functions to observations of RSGs in the SMC, LMC, and M31, restricting to $3.5<\log T_{\mathrm{e}\mathrm{f}\mathrm{f}}\mathrm{/}K<3.75$ and $\log (L\mathrm{/}{L}_{\odot })>4.5$. By-eye fits to the observations yield values of ${\xi }_{\mathrm{S}\mathrm{M}\mathrm{C}}=0.0-0.05$, ${\xi }_{\mathrm{L}\mathrm{M}\mathrm{C}}=0.1$, and ${\xi }_{\mathrm{M}31}=0.35$, implying a positive, linear trend between the strength of eruptive mass-loss and metallicity. This calibrated eruptive mass loss prevents stars with initial masses $\gtrsim 20M_{\odot }$ 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.