RR Lyrae Variables in Globular Clusters and Nearby Galaxies

Abstract

I point out that the Oosterhoff dichotomy for globular cluster and field RR Lyrae (RRL) stars may place the strongest constraints so far on the number of dwarf spheroidal-like protogalactic fragments that may have contributed to the formation of the Galactic halo. The first calibration of the RRL period-luminosity relation in I, J, H, K taking evolutionary effects into account is provided. Problems in the interpretation of RRL light curves and evolutionary properties are briefly reviewed.

Invited review, IAU Colloq. 193, "Variable Stars in the Local Group", ed. D. W. Kurtz & K. R. Pollard. ASP Conf. Ser., in press (11 pages, 3 figures). Replaced to match paper as it will appear in the conference proceedings volume. Includes Q&A section and a correction to Table 2