Theoretical models of Cepheid variables and their BVI(c) colors and magnitudes

In this paper we report a theoretical study of Cepheid variables. Large grids, containing in total about 6000 models, were calculated at varying mass, effective temperature, initial chemical composition, and mass-luminosity relation, the latter variable corresponding to different underlying evolutionary schemes for intermediate-mass stars, viz., classical models, models with mild core overshoot, and models with large core overshoot. The chemical abundances were chosen in order to bracket the abundances of the Cepheid stars in the Milky Way and in the Magellanic Clouds. The instability strips for three modes of pulsation (fundamental, first overtone, and second overtone) have been obtained, and analytical fits to the effective temperature and luminosity along the blue and red edges of the instability strips are presented