C- and O-Rich Miras and Galactic Structure

Abstract

This paper summarizes the conclusions of an extensive investigation of variable carbon AGB stars in our Galaxy. The zero-point of the period-M(bol) relation for Galactic C-Miras is found to be close to that in the LMC. The mean age of Galactic C-Miras is about 1.8 Gyr and their initial masses about 1.8 solar masses with some evidence that age decreases and initial mass increases with increasing pulsation period. Kinematic studies of Galactic C- and O-Miras show that the relative frequency of these two Mira classes depends on the age of the parent population. The lack of carbon stars in the Galactic Bulge seems due to a high oxygen abundance. The velocity dispersion of O-Miras allows one to distinguish between two possible models of Galactic kinematics.