THE ABSOLUTE MAGNITUDES OF THE RR LYRAE STARS

We present a new calibration of the relationship between the absolute magnitudes and metal abundances, [Fe/H], of RR Lyrae stars. Temperatur es inferred from optical and near-infrared color indices and the new K urucz models are utilized in conjunction with Baade-Wesselink solution s to derive absolute magnitudes. Temperatures inferred from the optica l and near-infrared photometry are similar to 200-300 K higher for the variables than those given from (V-K) color indices and the older Kur ucz models. We find M-v = 0.28[CFe/H] + 0.964. This equation gives hig her luminosities (similar to 0.2 mag) for the metal-poor variables tha n previous B-W calibrations. The RR Lyrae stars in the Large Magellani c Cloud in conjunction with our calibration yield a distance modulus o f 18.53. Thus, the Cepheids and RR Lyrae stars give identical distance moduli at less than or equal to 0.1 mag level. The repercussions of t he higher temperatures and higher luminosities of RR Lyrae stars on th e distances and ages of globular clusters, distance to the galactic ce nter, the Hubble constant and age of the Universe, and the masses of R R Lyrae stars are discussed.