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The Helium Abundance in the Envelopes of the Bluest RR Lyrae Stars in Globular Clusters and Dependence of Globular Cluster Variable Star Properties on Chemical Composition

Published online by Cambridge University Press:  12 April 2016

A. V. Mironov
A. V. Mironov*
Affiliation:
Tien-Shan High Mountain Observatory, Sternberg State Astronomical Institute, U.S.S.R.

Abstract

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The helium abundance Y in the envelopes of RR Lyrae stars in globular clusters has been estimated. The values of Y range from 0.07 to 0.59. The properties of variable stars in globular clusters of two types distinguished by a type of dependence of the horizontal branch form on the chemical composition are compared. The clusters of type I are shown to be on the average poorer in RR Lyrae stars than those of type II. The RR Lyrae stars in type I clusters are on the average brighter by 0.1 mag. It is found that as Y increases, the cluster richness in W Virginis variables decreases.

Type
Part IV / Theoretical Considerations of Population II Variables
Information
International Astronomical Union Colloquium , Volume 21: Variable Stars in Globular Clusters and in Related Systems , August 1973 , pp. 229 - 234
Copyright
Copyright © Reidel 1973

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