Distances and absolute magnitudes of RR Lyrae variable stars

Complete optical and infrared photometry were acquired for three fields RR Lyrae variables: the very metal-poor RRab-type variable X Arietis, the moderately metal-rich RRab star SW Draconis, and the moderately metal-rich RRc-type star DH Pegasi. Radial velocities with typical accuracies of 1 km sec-1 were also obtained for these stars nearly simultaneously with the photometry. Three versions of the Baade-Wesselink method were applied to these stars, and it was determined that only combinations involving the use of the V-K color index yielded self-consistent results, due to the occurrence of a redistribution of flux during the expansion phase of the pulsation cycle such that there is an excess of flux int eh blue optical region. Results for the three program stars indicate that there is no dependence of the value of (M/sub V/) of RR Lyrae stars upon their metallicity, although this is not definitive due to the unknown evolutionary status of these stars. The results imply that metal-poor globular clusters are older than metal-rich clusters, and that the oldest globular clusters may have an age of about 23 billion years