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A non-explanation of the Sandage effect: [CNO/Fe] ≠ 0

Published online by Cambridge University Press:  04 August 2017

Robert T. Rood
Robert T. Rood*
Affiliation:
Department of Astronomy, University of Virginia

Abstract

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In the log Te, log P' plot for RR Lyrae variables Sandage (1981) has noted that at a given color the period of the variables decreases as cluster metalicity increases. In particular the variables in M3 were shifted in log P' by 0.065 days compared to M15. The only explanation he could find for this shift was that Y in M3 was 0.05 less than in M15 and thus anticorrelated with Z. I have investigated the possibility that the shift is due to variations in [CNO/Fe]. At least for the range of [CNO/Fe] considered, it does not seem possible to explain the shift at constant Y.

Type
I. EVOLUTION OF LOW AND INTERMEDIATE MASS STARS OBSERVATIONS AND MODELS
Information
Symposium - International Astronomical Union , Volume 105: Observational Tests of the Stellar Evolution Theory , 1984 , pp. 167 - 170
Copyright
Copyright © Reidel 1984 

References

Rood, R. T. 1973, Ap. J., 184, 815.CrossRefGoogle Scholar
Rood, R. T., Seitzer, P. O. 1981, in Ap. Parms. of Globular Clusters, eds. Philip, A. G. D., Hayes, D. S., (Schenectady: L. Davis), p. 369.Google Scholar
Sandage, A. 1981, Ap. J., 248, 161.Google Scholar