Episodic Mass Loss and Pre-SN Circumstellar Envelopes

TL;DR

This paper reviews evidence that episodic mass loss from massive stars, especially LBVs, shortly before supernovae significantly influences their circumstellar environment and challenges existing stellar evolution models.

Contribution

It presents observational evidence linking LBV eruptions to supernova progenitors and discusses implications for stellar evolution theories.

Findings

LBVs are potential supernova progenitors during giant eruptions.

Episodic mass loss occurs within 5-10 years before some supernovae.

Massive stars can retain substantial hydrogen envelopes until explosion.

Abstract

I discuss observational clues concerning episodic mass-loss properties of massive stars in the time before the final supernova explosion. In particular, I will focus on the mounting evidence that LBVs and related stars are candidates for supernova progenitors, even though current paradigms place them at the end of core-H burning. Namely, conditions in the immediate circumstellar environment within a few 10$^2$ AU of Type IIn supernovae require very high progenitor mass-loss rates. Those rates are so high that the only known stars that come close are LBVs during rare giant eruptions. I will highlight evidence from observations of some recent extraordinary supernovae suggesting that explosive or episodic mass loss (a.k.a. LBV eruptions like the 19th century eruption of Eta Car) occur in the 5-10 years immediately preceding the SN. Finally, I will discuss some implications for stellar evolution from these SNe, the most important of which is the observational fact that the most massive stars can indeed make it to the ends of their lives with substantial H envelopes intact, even at Solar metallicity.