Dance to Demise -- How Massive Stars May Form Dense Circumstellar Shells Before Explosion

TL;DR

This paper models how red supergiant stars can develop dense circumstellar shells shortly before exploding as supernovae, explaining various observed phenomena in Type II supernovae.

Contribution

It introduces a detailed stellar evolution model incorporating pulsation-driven mass loss and shock ejections to predict dense CSM formation before supernova explosions.

Findings

Dense CSM shells form within decades before explosion.

Models match observed signatures in multiple Type II supernovae.

Enhanced mass loss episodes produce observable X-ray and radio emissions.

Abstract

We investigate the evolution of red supergiant (RSG) progenitors of core-collapse supernovae (SNe) with initial masses between $12$ and $20~\mathrm{M}_{\odot}$, focusing on effects of enhanced mass loss due to pulsation-driven instabilities in their envelopes and subsequent dynamical ejections during advanced stages of nuclear burning. Using time-dependent mass loss rates from detailed Modules for Experiments in Stellar Astrophysics (MESA) stellar evolution models, including prescriptions for both pulsation-driven superwinds and shock-induced ejections, we construct the circumstellar medium (CSM) before the SN explosion. We calculate resulting CSM density profiles and column densities considering the radiation-driven acceleration of the stellar wind. Our models produce episodes of enhanced mass loss $\sim 10^{-4}-10^{-2}~ \mathrm{M}_{\odot}~\mathrm{yr}^{-1}$ in the last centuries-decades before explosion forming dense CSM ($\gtrsim10^{-15}~\mathrm{g~cm}^{-3}$ at distances $\lesssim10^{15}~\mathrm{cm}$) - consistent with multi-wavelength observations of Type II SNe such as SN 2023ixf, SN 2020ywx, SN 2017hcc, SN 2005ip and SN 1998S. The formation of such dense CS shells, as predicted by our single star RSG models, provides a natural explanation for observed flash-ionization signatures, X-ray and radio emission, and has important implications for dust formation around Type II SNe.