Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

Theoretical prediction of surface stellar abundances light elements–lithium, beryllium, and boron–represents one the most interesting open problems in astrophysics. As well known, several measurements 7 Li atmospheres point out a disagreement between predictions observations different evolutionary phases, rising doubts about capability present models to precisely reproduce envelope characteristics. The problem takes aspects various phases; analysis is restricted protostellar pre-Main Sequence phases. Light elements are burned at relatively low temperatures ( T from ≈2 id="minf2">≈5 million degrees) thus early stages star they gradually destroyed depths interior mainly by (p, α) burning reactions, dependence on mass. Their strongly influenced nuclear cross sections, as extension toward convective temperature its bottom, which depend characteristics (mass chemical composition) energy transport envelope. In recent years, great effort has been made improve precision element sections. However, theoretical abundance challenging because also uncertainties input physics adopted calculations efficiency standard non-standard physical processes active young stars (i.e. diffusion, radiative levitation, magnetic fields, rotation). Moreover, it still not completely clear how much previous evolution affects depletion. This paper presents state-of-the-art for protostars their abundances, discussing role reaction rates other temporal predicted abundances.