Pulsational Instability Domains in the Upper Main Sequence

Updated theoretical instability domains in the Hertzsprung-Russell and in the log g-log Teff diagrams for the β Cep, the SPB and the δ Sct star models are presented. The position of the instability domains is very sensitive to the chemical composition parameters (X,Z) and to the extent (dover) of the convective overshooting, due to influence of these effects on the evolution, in particular, on the location of the Zero-Age Main Sequence (ZAMS) and the Terminal-Age Main Sequence (TAMS). Also, the heavy element abundance, Z, is of critical importance on the instability itself for the β Cep and the SPB models. The comparison of theoretical and observational domains may be used to constrain these parameters.