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Stellar evolution and period changes in RR Lyrae starsThe observed secular period changes of RR Lyrae stars in five globular clusters have been compared with those predicted by synthetic models of the horizontal branch (HB). It is shown that most of the observed number distributions of the period change rate beta could be attributed to evolutionary effects, if the random observational error is of order + or - 0.07 days/Myr in beta as suggested by the observers. The model calculations indicate that the mean rate of period change in RR Lyrae stars in globular clusters depends sensitively on their HB type, as is the case for the period shift at a given effective temperature. The distinct bias toward positive period changes in M15 and Omega Cen is evidence that most HB stars in the Oosterhoff group II clusters pass through the instability strip from blue to red toward the end of their core helium burning phase. If confirmed by future observations, this is strong support for the Lee et al. (1990) explanation of the Sandage (1957) period-shift effect.
Document ID
19910038066
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lee, Young-Wook
(Victoria, University Canada; Yale University, New Haven, CT, United States)
Date Acquired
August 15, 2013
Publication Date
February 1, 1991
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 367
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
91A22689
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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