RR LYRAE VARIABLE STARS: PULSATIONAL CONSTRAINTS RELEVANT TO THE OOSTERHOFF CONTROVERSY

Abstract

A solution to the old Oosterhoff controversy is proposed on the basis of a new theoretical pulsational scenario concerning RR Lyrae cluster variables (Bono and coworkers). We show that the observed constancy of the lowest pulsation period in both Oosterhoff type I (OoI) and Oosterhoff type II (OoII) prototypes (M3, M15) can be easily reproduced only by assuming the canonical evolutionary horizontal-branch luminosity levels of these Galactic globular clusters and therefore by rejecting the Sandage period shift effect (SPSE).

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• On the Impact of Helium Content on the RR Lyrae Distance Scale
• On the period distribution of cluster RR Lyrae stars to constrain their helium content: the case of omega Centauri
• A stellar population synthesis approach to the Oosterhoff dichotomy
• The RR Lyrae Distance Scale