Physical parameters of RR Lyrae stars in the globular cluster NGC 5466: The Oosterhoff dichotomy

Abstract

The highlights of CCD photometry of RR Lyrae stars in NGC 5466 are presented. The image subtraction method (Bramich et al. 2005) was used. The Fourier light curve decomposition, lead to an average [Fe/H]=-1.88+/-0.3 and a distance of 14.8+/-0.4 kpc for the cluster and to other physical parameters of astrophysical relevance for individual RR Lyrae stars. When a comparison of the mean physical parameters in globular clusters, analysed by the same technique, is performed, clear insights of the stellar evolution on the Horizontal Branch are obtained. The origin of the Oosterhoff dichotomy is clearly of evolutionary nature, being age the determining factor.