Keywords: Stars, physics, evolution, cepheids, pulsation.

Cepheids are pulsating stars hence they provide a very powerful diagnostic tool for probing stellar interiors. For several decades, they have given rise to a number of questions about the theory of evolution as well as stellar oscillations. The advent of massive microlensing experiments (EROS, OGLE, ...) of Magellanic Clouds have emphasized evolutionary and pulsation calculation for cepheids stars. The overshooting of the convective core plays an important role bringing the models towards blue loops stages, therefore I have developed an original method to determine the overshooting amount on convective core of SMC main sequence stars. I show that the overshooting amount is likely dependent on the chemical composition of stellar medium.

I first investigate the influence of several physical parameters on the evolution of low metallic cepheids. I show that the discrepancy disappears when the details of chemical composition are properly taken into account. I finally investigate the evolutionary properties of galactic cepheids. Although the pulsations of these stars are quite well known, the recent space observations with HST and IUE have provided new constraints for a few binary systems. The double-mode cepheid Y Carinae belongs to one of them. Here I propose the first fully satisfying modeling of both this star an its companion. On the other hand the resulting linear period ratio confirms the existence of shortcoming. Thus this system offers a new opportunity to signal us an subsisting imperfection of physical description.


My manuscript is available under two formats, the text is written 50%-50% in french and english: