SIMBAD references

We define the relationship between the double-mode pulsation of Cepheids and metallicity in a more accurate way, determine the empirical metallicities of double-mode Cepheids from homogeneous, high-resolution spectroscopic data, and study of the period-ratio - metallicity dependence. The high S/N echelle spectra obtained with the FEROS spectrograph were analyzed using a self-developed IRAF script, and the iron abundances were determined by comparing with synthetic spectra assuming LTE. Accurate [Fe/H] values of 17 galactic beat Cepheids were determined. All these stars have solar or slightly subsolar metallicity. Their period ratio (P₁/P₀) shows strong correlation with their derived [Fe/H] values. The corresponding period ratio - metallicity relation has been evaluated.