Envelope inflation in Wolf-Rayet stars and extended supernova shock breakout signals

TL;DR

This paper explores how envelope inflation in Wolf-Rayet stars can lead to extended supernova shock breakout signals, potentially explaining unusually long observed signals like in SN 2008D.

Contribution

It demonstrates that inflated, hydrogen-free Wolf-Rayet star models can produce shock breakout signals longer than 60 seconds, linking envelope inflation to observable supernova features.

Findings

Inflated WR star models can have shock breakout signals >60 seconds.

Long shock breakout signals, like in SN 2008D, can be explained by envelope inflation.

Inflated envelopes may be common in WR progenitors of Type Ib/c supernovae.

Abstract

Massive, luminous stars reaching the Eddington limit in their interiors develop very dilute, extended envelopes. This effect is called envelope inflation. If the progenitors of Type Ib/c supernovae, which are believed to be Wolf-Rayet (WR) stars, have inflated envelopes then the shock breakout signals diffuse in them and can extend their rise times significantly. We show that our inflated, hydrogen-free, WR stellar models with a radius of ~Rsun can have shock breakout signals longer than ~60 s. The puzzlingly long shock breakout signal observed in the Type Ib SN 2008D can be explained by an inflated progenitor envelope, and more such events might argue in favour of existence of inflated envelopes in general.