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Period Changes of RR Lyrae Stars in Seven Globular Clusters
Pamela Gay Rathbun and Horace A. Smith
Publications of the Astronomical Society of the Pacific
Vol. 109, No. 740 (1997 October), pp. 1128-1134
Published by: Astronomical Society of the Pacific
Stable URL: http://www.jstor.org/stable/40681009
Page Count: 7
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We have used data from the literature to reexamine the period changes of RR Lyrae variables in the globular clusters M3, M4, M5, M15, M22, NGC 6934, and NGC 7006. There is a tendency for the more extreme rates of period change to be found in RRab rather than RRcd stars. Particularly absent from the RRcd star sample are stars showing large rates of period decrease, a result which may in part reflect the small proportion of RRcd variables in Oosterhoff I clusters. The apparent coupling of period change to pulsation mode is not easily interpreted as an evolutionary effect, and appears to be without adequate explanation.
Publications of the Astronomical Society of the Pacific © 1997 The University of Chicago Press