Advancements in the Stellar Evolution Theory: The Role of Convective Overshooting All Across the HR Diagram

Abstract

In this paper we present recent calculations of stellar structure in which the effects of convective overshooting are taken into account during the core H- and He-burning phases of stars in the mass range 1.3 M_⊙ to 100 M_⊙. In addition to this, we briefly review the effects of mass loss in luminous stars of all spectral types, and in red giant and asymptotic giant branch stars. Finally, the effects of the novel cross section for the ¹²C(α,γ)¹⁶O nuclear reaction are also illustrated.

The main purpose of this review resides however in lending convincing support to the idea that convective cores of real stars are greater than commonly supposed in classic models. To this aim, several observational facts that could not be explained by classic models are reanalyzed in the light of the new ones. Since a much better agreement between theory and observations is now possible, we are inclined to conclude that convective overshooting may be of paramount importance in theories of stellar structure and that convective cores in real stars ought to be larger by approximately one pressure scale height than predicted by classic models. The implications of these new stellar models in theoretical models of photometric evolution of galaxies are numerous and easy to foresee.