Red variables in globular clusters - Their classification and evidence for mass loss

The classification scheme for red long-period variables (LPVs) in globular clusters is reexamined, and evidence for mass loss in these stars is investigated. It is found that the long-period and peculiar variables in globular clusters define classes of stars distinct from the other stars in the clusters. The variables are characterized by high luminosities, without exception above that required for core helium flash, and are the only cluster stars to be so luminous. They have excess infrared emission indicative of high mass-loss rates and excess H2O absorption in their atmospheres, indicative of significant differences in the structure of the outer atmospheres of the variable stars as compared with nonvariables. The mass-loss rates for the cluster LPVs are comparable to those calculated for metal-rich solar neighborhood stars with significantly greater infrared excesses. This implies that pulsation plays a key role in the mass loss.