Frequency and evolutionary impact of massive star mergers

Determine the frequency of mergers occurring prior to explosion among massive stars with initial mass at least 8 solar masses and characterize the effects of such mergers on the stellar evolution of massive stars.

Background

The paper discusses that massive stars (≥8 M⊙) can undergo mergers before their terminal explosions, but observational constraints on how common these events are and their consequences for stellar evolution remain sparse. Given that over 90% of massive stars exist in multiple systems, quantifying the occurrence rate of pre-explosion mergers is crucial for understanding massive-star evolutionary pathways, compact-object formation, and feedback into galaxies.

This paper provides evidence of a recent merger in the HD 148937 system and shows how such an event can produce both a magnetic massive star and a bipolar nebula. However, it does not resolve the broader population-level questions about merger frequency and evolutionary impacts, which remain explicitly identified as unclear.