Department of Physics and Astronomy: Publications and Other Research

 

Document Type

Article

Date of this Version

1990

Citation

Confrontation Between Stellar Pulsation and Evolution, ASP Conference Series, Vol. 11, 1990, C. Cacciari and G. Clementini, Eds., pp. 416-420.

Comments

Copyright 1990 Astronomical Society of the Pacific. Provided by the NASA Astrophysics Data System.

Abstract

The theory of horizontal branch (HB) evolution predicts the masses of RR Lyrae stars in globular clusters. These masses depend on metallicity according to a relation which can be expressed in the form (Sandage 1990):

log M(RR) = -0.10 [Fe/H] - 0.318.

Equation (1) describes the zero age HB models of both Sweigart, Renzini and Tornambe (1987) and Lee, Demarque and Zinn 1990 (hereinafter LDZ).

Using Eq. (1) we may calculate approximate RR Lyrae masses for the Oosterhoff groups. For an 0o I cluster like M3 one finds M(RR) ~ 0.71 Mʘ , while an 0o II cluster like M15 gives M(RR) ~ 0.82 Mʘ. These masses are in disagreement with the considerably smaller values derived from linear, nonadiabatic (LNA) pulsation models for the RRd stars (double mode pulsators), viz., M(RR) ~ 0.55 Mʘ for 0o I clusters and M(RR) ~ 0.65 Mʘ for 0o II clusters (Cox, Hodson and Clancy 1983).

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