Some Problems in the Study of Variable Stars in Globular Clusters

Abstract

Three quarters of a century separates us from the beginning of systematic observations of variable stars in globular clusters. During the last 45 yr the name of Mrs Prof. Dr H. B. Sawyer Hogg has always been in the astronomical literature. Her activity is closely connected with investigations of variable stars in globular clusters.The complex dependences between the presence of variable stars of different types and the properties of the globular clusters were discovered long ago. For instance, the RR Lyr variables do not occur in clusters of high metallicity. Red variables on the contrary do not occur in clusters of very low metallicity. The presence and peculiarities of variable stars have been used for the classification of globular clusters (van Agt and Oosterhoff, 1959; Castellani et al., 1970).