RR Lyrae Stars: Period-Luminosity Relations and Oosterhoff Groups

Smith, H. A.; Pritzl, B. J.; Catelan, Marcio; Sweigart, A. V.; De Lee, N.; Contreras, R.

RR Lyrae Stars: Period-Luminosity Relations and Oosterhoff Groups

Date

2003

Authors

Abstract

We use new observations and data from the literature to construct I band period-luminosity relations for RR Lyrae stars in globular clusters. We present synthetic horizontal branches made from theoretical evolutionary models to understand better the effect which horizontal branch morphology has upon the period-luminosity relations in I and several other passbands. We also use the observed relations to address the question of the prevalence of second overtone pulsators among the RR Lyrae stars. We will review an ongoing observational program designed to obtain photometry for variable stars in globular clusters that show the second parameter effect and that cannot be easily placed within the two usual Oosterhoff groups. We thank the National Science Foundation for partial support of this work....