Open questions in massive star research

TL;DR

This paper reviews key open questions in massive star research, covering their formation, evolution near the Eddington limit, binary interactions, and explosive endpoints like supernovae.

Contribution

It synthesizes current uncertainties and highlights areas needing further investigation in the evolution and end stages of massive stars.

Findings

Massive star formation may be bimodal and not always lead to a zero-age main sequence.

Binary interactions significantly influence the evolution and end states of massive stars.

Understanding pair instability supernovae and superluminous supernovae remains a key open challenge.

Abstract

In discussing open question in the field of massive stars, I consider their evolution from birth to death. After touching upon massive star formation, which may be bi-modal and not lead to a zero-age main sequence at the highest masses, I consider the consequences of massive stars being close to their Eddington limit. Then, when discussing the effects of a binary companion, I highlight the importance of massive Algols and contact binaries for understanding the consequences of mass transfer, and the role of binaries in forming Wolf-Rayet stars. Finally, a discussion on pair instability supernovae and of superluminous supernovae is provided.