Computation of the Fourier parameters of RR Lyrae stars by template fitting
1
Konkoly Observatory, PO Box 67, 1525 Budapest, Hungary e-mail: kovacs@konkoly.hu
2
ARI, Heidelberg, Germany e-mail: kupiga@ari.uni-heidelberg.de
Received:
16
July
2006
Accepted:
21
September
2006
Aims.Due to the importance of accurate Fourier parameters, we devise a method that is more appropriate for deriving these parameters for low-quality data than the traditional Fourier fitting.
Methods.Based on the accurate light curves of 248 fundamental mode RR Lyrae stars, we test the power of a full-fetched implementation of the template method in the computation of the Fourier decomposition. The applicability of the method is also demonstrated on data sets of filter passbands different from those of the template set.
Results.We examine in more detail the question of the estimation of
Fourier-based iron abundance [Fe/H] and average brightness.
We get, for example, for light curves sampled randomly in 30 data
points with 
mag observational noise, that optimized
direct Fourier fits yield 
, whereas the
template fits result in 
. Tests made on
the RR Lyrae database of the Large Magellanic Cloud of the
Optical Gravitational Lensing Experiment support the
applicability of the method on real photometric time series. These
tests also show that the dominant part of error in estimating the
average brightness comes from other sources, most probably from
crowding effects, even for under-sampled light curves.
Key words: methods: data analysis / stars: variables: RR Lyr / stars: fundamental parameters
© ESO, 2007