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An RR Lyrae period shift in terms of the Fourier parameter Phi sub 31The Fourier phase parameter Phi sub 31 has been determined for RRc stars in five globular clusters, NGC 6171, M5, M3, M53, and M15. The results indicate that the RRc stars in a given cluster show a sequence of Phi sub 31 increasing with period, and that the higher the cluster metallicity, the higher the sequence lies in a plot of Phi sub 31 with period. The Phi sub 31 values for the stars in NGC 6171 and M5 presented here are based on observations made with the University of Toronto 0.61 m telescope at Las Campanas, Chile, while those for M3, M53, and M15 are based on published data. A bootstrap procedure has been used to establish the uncertainties in the Fourier parameters. The physical significance of the relationship among Phi sub 31, period, and metallicity is not yet understood. It will need to be tested with hydrodynamic pulsation models computed with new opacities.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Clement, Christine M. (NASA Headquarters Washington, DC United States)
Jankulak, Michael (David Dunlap Observatory Toronto, Canada)
Simon, Norman R. (Nebraska Univ. Lincoln, United States)
Date Acquired
August 15, 2013
Publication Date
August 10, 1992
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 395
Issue: 1
ISSN: 0004-637X
Subject Category
Funding Number(s)
Distribution Limits