A NEW METHOD FOR THE DETERMINATION OF [FE H] IN RR LYRAE STARS/

The Fourier parameters of the V light curves of the field RRab stars a re used to fit their [Fe/H]. The method is based on the assumption tha t the observed light curves depend only on a few physical parameters, including the chemical composition. We give two formulae which estimat e the observed [Fe/H] with an accuracy of 0.23-0.18 dex. Each of these expressions consists of a second order polynom of 2-4 Fourier paramet ers and the period. The method is a powerful tool in estimating the me tallicity when spectroscopic data are not available.