Red Supergiants, Yellow Hypergiants, and Post-RSG Evolution

TL;DR

This paper reviews recent observational and modeling studies on post-RSG stars, exploring their evolution, mass-loss events, and connections to other massive star types like LBVs and hypergiants.

Contribution

It synthesizes recent findings on the characteristics and evolution of post-RSG stars, emphasizing their role in massive star life cycles.

Findings

Post-RSG stars show evidence of high mass-loss episodes.

Connections between post-RSGs, LBVs, and hypergiants are explored.

Mass-loss history significantly influences the final stages of massive stars.

Abstract

How massive stars end their lives remains an open question in the field of star evolution. While the majority of stars above 9 M_sun will become red supergiants (RSGs), the terminal state of these massive stars can be heavily influenced by their mass-loss histories. Periods of enhanced circumstellar wind activity can drive stars off the RSG branch of the HR Diagram. This phase, known as post-RSG evolution, may well be tied to high mass-loss events or eruptions as seen in the Luminous Blue Variables and other massive stars. This article highlights some of the recent observational and modeling studies that seek to characterize this unique class of stars, the post-RSGs, and link them to other massive objects on the HR Diagram such as LBVs, Yellow Hypergiants, and dusty RSGs.