Abstract

Wolf-Rayet (WR) stars are an advanced evolutionary stage of some massive stars, with very hot temperatures and high wind mass-loss rates inferred from their spectra. Observed WR stars are thought to have cores too massive to explode, and therefore collapse to black holes with no supernova at the end of their evolution. Yet, some hydrogen-poor supernovae exhibit spectral signatures indicating the progenitor star had a wind reminiscent of WR stars. I propose that most of the exploding WR stars are not those that are observed, but rather less massive helium stars whose hydrogen envelope was stripped by binary interaction. The wind mass-loss rate of these stripped stars becomes high only in their final evolutionary stages, after core helium burning has ended. Using detailed binary stellar evolution simulations, I show that the evolution of stripped stars can end in a short-lived WR phase of only a few millennia, in contrast to hundreds of millennia of their more massive WR siblings. Such lightweight WR stars can account for observed properties of type Ib/c supernovae. Employing a population synthesis approach, accounting for the formation likelihood and lifetimes, I show that the majority of exploding WR stars are the minority of living WR stars.