The Oosterhoff period groups and the age of globular clusters. I Photometry of cluster variables in M15

Abstract

view Abstract Citations (221) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Oosterhoff period groups and the age of globular clusters. I. Photometry of cluster variables in M 15. Sandage, A. ; Katem, B. ; Sandage, M. Abstract Three-color photometry is used to study distributions of color, amplitudes, light-curve shapes, and periods within the instability strip of 60 RR Lyrae stars in M15. Period-amplitude, period-rise time, period-color, and color-amplitude relations are compared with data for M3, and correlations of parameters involving period are shifted by delta log P = 0.055 to longer periods in M15. An M15 horizontal branch brighter than that in M3 by delta log L(HB) = 0.090 is found to be the only explanation consistent with the Ritter condition. The abundance is shown to differ between the clusters by delta Y(M15 minus M3) = +0.05 + or - 0.02 using zero-age horizontal branch models, and the ages of M3 and M15 are shown the same within 0.5 sigma of the combined error. The mean age is found using Iben-Rood and Yale models, and HB luminosity and metallicity is found to be the same as required for main-sequence turnoff luminosity for two clusters of same age and different metallicities. Publication: The Astrophysical Journal Supplement Series Pub Date: May 1981 DOI: 10.1086/190734 Bibcode: 1981ApJS...46...41S Keywords: Abundance; Globular Clusters; Stellar Evolution; Stellar Spectrophotometry; Variable Stars; Color; Helium; Horizontal Branch Stars; Light Curve; Main Sequence Stars; Metallic Stars; Stellar Luminosity; Tables (Data); Astrophysics full text sources ADS | data products SIMBAD (67)