Delta Scuti, SX Phoenicis, and RR Lyrae Stars in Galaxies and Globular Clusters

The distances to four galaxies and two globular clusters which are derived with the aid of period-luminosity and period-color relations of Delta *d Scuti and SX Phe stars are compared to the distances derived by other methods, in particular RR Lyrae stars. We examine the luminosities of horizontal b...

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Bibliographic Details
Published in:The Astronomical journal 2011-10, Vol.142 (4), p.110-jQuery1323897012192='48'
Main Author: McNamara, D. H
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Clusters
COLOR
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
Globular clusters
Iron
LUMINOSITY
MAGELLANIC CLOUDS
Mathematical analysis
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
STAR EVOLUTION
Star formation
STARS
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Summary:The distances to four galaxies and two globular clusters which are derived with the aid of period-luminosity and period-color relations of Delta *d Scuti and SX Phe stars are compared to the distances derived by other methods, in particular RR Lyrae stars. We examine the luminosities of horizontal branch or RR Lyrae stars in Oosterhoff I and II globular clusters. Observational data from a variety of sources indicate a discontinuous jump of ~0.2 mag in the luminosities of RR Lyrae variables at [Fe/H] --1.5 as we transition from Oosterhoff I to Oosterhoff II clusters. If Oosterhoff I clusters have RR Lyrae variables with average M V values of M V = 0.53 mag at [Fe/H] = --1.5, it implies that RR Lyrae stars in Oosterhoff II clusters average M V values are ~0.34 mag. Unlike the Oosterhoff I clusters which show an increase in the V luminosity of RR Lyrae stars as [Fe/H] becomes smaller, little or no change in the V luminosity of RR Lyrae variables is evident in Oosterhoff II clusters in the interval of [Fe/H] from --1.5 to --2.2. We find distance moduli found with RR Lyrae variables agree to
ISSN:1538-3881
0004-6256
1538-3881
DOI:10.1088/0004-6256/142/4/110