A Search for Long-Period Variables in Globular Clusters: M22 and IC4499

Abstract

AbstractWe report on the results of a long time photometric monitoring of the two metal-poor Galactic globular clusters, M22 and IC4499, searching for long-period variables (LPVs) on the upper giant branch. We detected 22 new LPVs in the field of M22 and confirmed the variability of six known variables. Periods could be determined for 16 of them. In the field of IC4499 we detected and characterised two new LPVs. Cluster membership is evaluated for all the variables based on photometry and literature data, and the location of the stars in logP-K-diagram is discussed. Our findings give further support to the presence of LPVs at metallicities as low as [Fe/H] = −1.7. The luminosity range where LPVs are found in metal-poor clusters is lower than in more metal-rich clusters.