THE ABSOLUTE MAGNITUDES OF THE RR LYRAE STARS

Abstract

ABSTRACT We present a new calibration of the relationship between the absolute magnitudes and metal abundances, [Fe/H], of RR Lyrae stars. Temperatures inferred from optical and near infrared color indices and the new Kurucz models are utilized in conjunction with Baade-Wesselink solutions to derive absolute magnitudes. Temperature inferred from the optical and near infrared photometry are ∼ 200K - 300K higher for the variables than those given from (V-K) color indices and the older Kurucz models. We find Mv = 0.287 [Fe/H] + 0.964. This equation gives higher luminosities (∼ 0.2 mag) for the metal-poor variables than previous B-W calibrations. The RR Lyrae stars in the Large Magellanic Cloud in conjunction with our calibration yield a distance modulus of 18.53. Thus, the Cepheids and RR Lyrae stars give identical distance moduli at ≤q 0.1 mag level. The repercussions of the higher temperatures and higher luminosities of RR Lyrae stars on the distances and ages of Globular clusters, distance to the galactic center, the Hubble constant and age of the universe, and the masses of RR Lyrae stars are discussed.