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A&A 371, 579-591 (2001)
DOI: 10.1051/0004-6361:20010346
Empirical relations for cluster RR Lyrae stars revisited
G. Kovács1 and A. R. Walker21 Konkoly Observatory, PO Box 67, 1525 Budapest, Hungary
2 Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory (The National Optical Astronomy Observatory is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Fundation.) , Casilla 603, Chile
e-mail: awalker@noao.edu
(Received 2 January 2001 / Accepted 28 February 2001 )
Abstract
Our former study on the empirical relations between the Fourier parameters
of the light curves of the fundamental mode RR Lyrae stars and their basic
stellar parameters has been extended to considerably larger data sets.
The most significant contribution to the absolute magnitude MV comes
from the period P and from the first Fourier amplitude A1, but there
are statistically significant contributions also from additional higher
order components, most importantly from A3 and in a lesser degree from
the Fourier phase
. When different colors are combined in
reddening-free quantities, we obtain basically period-luminosity-color
relations. Due to the
![$\log T_{\rm eff}(B-V,\log g,{\rm [Fe/H]})$](/articles/aa/abs/2001/20/aa10638/img2.gif){kind=small}
relation
from stellar atmosphere models, we would expect some dependence also on
. Unfortunately, the data are still not extensive and
accurate enough to decipher clearly the small effect of this Fourier
phase. However, with the aid of more accurate multicolor data on
field variables, we show that this Fourier phase should be present
either in V-I or in B-V or in both. From the standard deviations
of the various regressions, an upper limit can be obtained on the
overall inhomogeneity of the reddening in the individual clusters.
This yields
mag, which also implies
an average minimum observational error of
mag.
Key words: stars: fundamental parameters -- stars: distances -- stars: variables -- stars: oscillations -- stars: horizontal-branch -- globular clusters: general
Offprint request: G. Kovács, kovacs@konkoly.hu
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