NONLINEAR MODELS OF 1ST OVERTONE MODE CEPHEIDS

Nonlinear models of population I Cepheids pulsating in the first overt one mode have been constructed using augmented opacities and a nonstan dard mass-luminosity relation. The properties of the Fourier parameter s of their light curves are discussed and compared with those of obser ved stars. It is shown that the models reproduce in part the observed behavior of first overtone Cepheids, and confirm the importance of the resonance P1/P4=2 between the first and fourth overtone modes.