Episodic mass loss in extreme Red Supergiants

Abstract: Red Supergiants (RSGs) are cool, evolved massive stars (8–30 M⊙) that represent the final evolutionary phase before a Type II supernova. However, the absence of luminous RSGs as confirmed SN progenitors has raised a sparkling debate about their fate. Mass loss is a critical factor in their evolution, and recent discoveries of large episodic mass-loss events suggest an alternative mechanism beyond steady winds. Yet, the frequency and impact of such episodes remain uncertain. In this work, we investigate two extreme RSGs using long-term photometry and multi-epoch spectroscopy. We find that [W60] B90 shows recurrent dimming events, consistent with episodic mass loss, and may be a more massive, subsolar metallicity analog of Betelgeuse. We also report a dramatic transformation in WOH G64, the most extreme RSG in the LMC. It recently transitioned into a Yellow Hypergiant in a fast, yet smooth transition. We identify it as part of a massive symbiotic system and propose that this evolution may result from a decades-long silent eruption or partial atmospheric ejection during a common-envelope phase. These findings challenge existing models of massive star evolution and highlight the need for further observational constraints.