# Pre-Supernova Outbursts via Wave Heating in Massive Stars I: Red Supergiants

## TL;DR

This study models how wave-driven energy transport in late-stage red supergiants causes mild pre-supernova outbursts and envelope inflation, influencing supernova diversity and early observations.

## Contribution

It introduces detailed stellar evolution models showing wave heating effects in red supergiants prior to supernova, a novel mechanism for pre-SN outbursts.

## Key findings

- Waves carry about 10^7 L_sun of power during core neon/oxygen burning.
- Wave damping causes mild outbursts and small mass ejection (~1 M_sun) about one year before collapse.
- Wave heating inflates the envelope, affecting pre-SN structure and supernova appearance.

## Abstract

Early observations of supernovae (SNe) indicate that enhanced mass loss and pre-SN outbursts may occur in progenitors of many types of SNe. We investigate the role of energy transport via waves driven by vigorous convection during late-stage nuclear burning of otherwise typical $15 \, M_\odot$ red supergiant SNe progenitors. Using MESA stellar evolution models including 1D hydrodynamics, we find that waves carry $\sim \! 10^7 \, L_\odot$ of power from the core to the envelope during core neon/oxygen burning in the final years before core collapse. The waves damp via shocks and radiative diffusion at the base of the hydrogen envelope, which heats up fast enough to launch a pressure wave into the overlying envelope that steepens into a weak shock near the stellar surface, causing a mild stellar outburst and ejecting a small ($\lesssim 1 \, M_\odot$) amount of mass at low speed ($\lesssim \! 50 \, {\rm km}/{\rm s}$) roughly one year before the SN. The wave heating inflates the stellar envelope but does not completely unbind it, producing a non-hydrostatic pre-SN envelope density structure different from prior expectations. In our models, wave heating is unlikely to lead to luminous type IIn SNe, but it may contribute to flash-ionized SNe and some of the diversity seen in II-P/II-L SNe.