The Topology of the RR Lyrae Instability Strip and the Oosterhoff Dichotomy
Citations Over TimeTop 22% of 1995 papers
Abstract
Convective pulsating models with Y = 0.24, stellar mass M = 0.65 Msun, and M = 0.75 Msun, under selected assumptions about luminosities and effective temperatures, are used together with stellar atmosphere computations to get the predicted dependence of RR Lyrae instability strip on stellar mass in the observative plane (MV, B - V). The comparison with observed variables belonging to the globular clusters M3 and M 15 is presented. It appears that in M3 (Oosterhoff type I) the transition between a b-type and c-type RR Lyrae takes place along the fundamental blue edge, whereas in M 15 (Oosterhoff type II) it occurs near the first overtone red edge. This result supports the key role of the hysteresis mechanism originally proposed by van Albada & Baker for explaining the Oosterhoff dichotomy.