The absolute magnitudes of LMC RR Lyrae variables and the ages of Galactic globular clusters

Abstract

From CCD photometry for a total of 182 RR Lyrae variables in seven Large Magellanic Cloud clusters, and color-magnitude diagrams for the clusters themselves, mean magnitudes for the variables, abundances and reddenings have been determined. For an LMC modulus of 18.5 m, the RR Lyraes are found in the mean to have = 0.44 at [Fe/H] = -1.9, some 0.3 m brighter than suggested by statistical parallax analyses of Galactic field RR Lyraes and from parallaxes of subdwarfs. The consequences of this result on Galactic distances and the ages of globular clusters are discussed