Uncertainty in envelope removal of core-collapse supernova progenitors

The theoretical modeling of massive star evolution is riddled with uncertainties. Two such unresolved aspects are mass loss by stellar winds and mixing in stellar interiors. In my talk I will discuss the implications of these uncertainties on reconciling theory with observations of massive stellar endpoints. In the first part I will present the role of winds for progenitors of stripped-envelope supernovae. While it is commonly assumed that binary interaction removes the hydrogen envelope, the assumed post-interaction mass-loss rate is crucial for the resulting supernova type. I will show how we assess the hydrogen mass in stripped-envelope supernova progenitors by comparing pre-supernova photometry with evolution models. In the second part of the talk I will focus on the lack of observed cool and very luminous supergiant stars, an unexplained phenomenon termed the “Humphreys-Davidson Limit”, which is in contrast to simulations of evolved massive stars. I will show how enhanced mixing above convective cores can aid in removing the hydrogen envelope and ease the tension between theory and observations for such stars at the high-mass end, which are also thought to be the progenitors of merging black holes.