Abstract:
We describe and summarize the findings from our CCD time-seri
es photom-
etry of globular clusters (GCs) program and the use of differe
nce image analysis
(DIA) in the extraction of precise light curves down to
V
≈
19 mag in crowded
regions. We have discovered approximately 250 variable sta
rs in a sample of 23
selected GCs. The absolute magnitude and [Fe/H] for each ind
ividual RR Lyrae
is obtained via the Fourier decomposition of the light curve
. An average of these
parameters leads to the distance and metallicity of the host
GCs. We present the
mean [Fe/H],
M
V
and distance for 26 GCs based exclusively on the RR Lyrae ligh
t
curve Fourier decomposition technique on an unprecedented
homogeneous scale.
We also discuss the luminosity dependence of the horizontal
branch (HB) via the
M
V
-[Fe/H] relation. We find that this relation should be consid
ered separately for
the RRab and RRc stars.
