The Chemical Composition of B-type Pulsators: Some Unexpected Results

We present a project aimed at self-consistently deriving the physical parameters and chemical composition of massive pulsators (β, Cephei stars, Slowly Pulsating B stars) based on high-resolution optical spectra. Such data will be essential for a proper theoretical interpretation of their oscillation spectrum, but may also contribute in a broader context to our understanding of mixing and diffusion processes in B-type stars. As an illustration, our first results reveal the existence of core-processed material at the surface of some slowly-rotating β, Cephei stars which is not predicted by current evolutionary models including rotation.