1995A&A...302..105A

Light and radial velocity curves of observed first overtone mode Cepheids have been compared with the curves of nonlinear models constructed using the new opacities. The study confirms that the characteristics of the curves depend on the resonance P₁/P₄=2 between the first and the fourth overtone mode. However, discrepancies and systematic differences between theory and observations are still present. It is shown that the diagrams of amplitude ratios R₂₁ and phase difference φ₂₁ of light curves versus the period are sensitive to the T_e of the models. Interesting properties of the phase lag between light and radial velocity curve are also discussed.