Pre-Supernova evolution of massive stars

We present the preliminary results of a detailed theoretical investigation on the hydrodynamical properties of Red Supergiant (RSG) stars at solar chemical composition and for stellar masses ranging from 10 to 20 MD. We find that the main parameter governing their hydrodynamical behavior is the effective temperature, and indeed when moving from higher to lower effective temperatures the models show an increase in the dynamical perturbations. Also, we find that RSGs are pulsationally unstable for a substantial portion of their lifetimes. These dynamical instabilities play a key role in driving mass loss, thus inducing high mass loss rates (up to almost 10(-3) M-circle dot yr(-1)) and considerable variations of the mass loss activity over timescales of the order of 10(4) years. Our results are able to account for the variable mass loss rates as implied by radio observations of type Il supernovae, and we anticipate that comparisons of model predictions with observed circumstellar phenomena around SNII will provide valuable diagnostics about their progenitors and their evolutionary histories.