T Ursae Minoris: From Mira to ??? (Abstract)

Volume 38 number 1 (2010)

Grant Foster

Abstract

(Abstract only) T UMi is known to have decreased its period and amplitude dramatically, perhaps due to a helium shell flash. Most recently, its amplitude has dropped below the limit defining the class of Mira-type variables, and it now shows signs of multimode pulsation, the two modes having the period ratio observed in many semiregular variables. We suggest that T UMi is no longer a Mira-type variable, instead it is presently behaving like a member of the SRb class.