The Circumstellar Environments of the Cool Hypergiants: Implications for the Mass Loss Mechanism

Abstract

The cool hypergiants are the most luminous known stars in the upper HR Diagram in the apparent temperature range represented by the spectral types A to M. Most of these stars in this regime are unstable as evidenced by their high mass loss rates, variability, and in some cases large IR excesses and circumstellar ejecta. In this brief paper, I describe the complex circumstellar ejecta of two remarkable hypergiants IRC+10420 and VY CMa and the evidence for high mass loss episodes in their recent history apparently driven by large-scale convective activity.