  Red supergiants (RSGs) are a He-burning phase in the evolution of moderately
high mass stars (10-25 solar masses). The evolution of these stars,
particularly at low metallicities, is still poorly understood. The latest-type
RSGs in the Magellanic Clouds are cooler than the current evolutionary tracks
allow, occupying the region to the right of the Hayashi limit where stars are
no longer in hydrodynamic equilibrium. We have discovered four Cloud RSGs in
this region that display remarkably similar unusual behavior. All of them show
considerable variations in their V magnitudes and effective temperatures (and
spectral types). Two of these stars, HV 11423 and [M2002] SMC 055188, have been
observed in an M4.5 I state, considerably later and cooler than any other
supergiant in the SMC. These stars suffer dramatic physical changes on
timescales of months - when they are at their warmest, they are also brighter,
more luminous, and show an increased amount of extinction. This variable
extinction is characteristic of the effects of circumstellar dust, and can be
connected with sporadic dust production from these stars in their cooler
states. We suggest that these unusual properties are indicative of an unstable
(and short-lived) evolutionary phase not previously associated with RSGs, and
consider the implications such behavior could have for our understanding of the
latest stages of massive star evolution in low-metallicity environments.
