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A Preliminary Investigation of Period Changes For W Virginis Stars in Globular Clusters

Published online by Cambridge University Press:  12 April 2016

Christine M. Coutts
Christine M. Coutts*
Affiliation:
David Dunlap Observatory, University of Toronto, Richmond Hill, Ontario, Canada

Extract

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Investigations in recent years have shown that there may be two mechanisms which place stars in the W Virginis instability region (Kraft, 1972). The variables with periods less than 8 days seem to be in the stage of ‘above horizontal branch’ evolution discussed by Strom et al. (1970). The longer period group apparently results when thermal instabilities in the helium burning shell of an asymptotic red giant branch star cause it to loop to the left in the HR diagram. This longer period group has been investigated by Schwarzschild and Härm (1970) and Mengel (1972). The present study has been undertaken to see if there are any notable differences between the period changes of variables belonging to the two groups.

Type
Part III / Slow Variables in Population II Systems
Information
International Astronomical Union Colloquium , Volume 21: Variable Stars in Globular Clusters and in Related Systems , August 1973 , pp. 145 - 149
Copyright
Copyright © Reidel 1973

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