Wave-Driven Mass Loss in the Last Year of Stellar Evolution: Setting the Stage for the Most Luminous Core-Collapse Supernovae

TL;DR

This paper proposes that wave-driven mass loss caused by internal gravity and sound waves in massive stars' late stages can explain the large circumstellar material observed in some supernovae, impacting stellar evolution models.

Contribution

It introduces a mechanism where gravity waves convert into sound waves, leading to significant mass loss just before core-collapse in massive stars.

Findings

Wave energy flux exceeds Eddington luminosity during last years of stellar life.

Conversion of gravity waves into sound waves can unbind several solar masses of stellar envelope.

This process explains observed large mass loss rates in certain supernovae types.

Abstract

During the late stages of stellar evolution in massive stars (C fusion and later), the fusion luminosity in the core of the star exceeds the star's Eddington luminosity. This can drive vigorous convective motions which in turn excite internal gravity waves. The local wave energy flux excited by convection is itself well above Eddington during the last few years in the life of the star. We suggest that an interesting fraction of the energy in gravity waves can, in some cases, convert into sound waves as the gravity waves propagate (tunnel) towards the stellar surface. The subsequent dissipation of the sound waves can unbind up to several $M_\odot$ of the stellar envelope. This wave-driven mass loss can explain the existence of extremely large stellar mass loss rates just prior to core-collapse, which are inferred via circumstellar interaction in some core-collapse supernovae (e.g., SNe 2006gy and PTF 09uj, and even Type IIn supernovae more generally). An outstanding question is understanding what stellar parameters (mass, rotation, metallicity, age) are the most susceptible to wave-driven mass loss. This depends on the precise internal structure of massive stars and the power-spectrum of internal gravity waves excited by stellar convection.