Constraints on Stellar Hydrodynamics from Abundance Anomalies of LiBeB and Metals

Abstract

The availability of large atomic data bases has made it possible to calculate stellar evolution models taking into detailed account the atomic diffusion of all important contributors to opacity. The radiative accelerations and the opacity are continuously calculated during evolution taking the abundance changes of 28 species into account. This leads to the first self-consistent stellar evolution models for A and F stars. In A and F stars an iron-peak convection zone appears.The calculated abundance anomalies are very similar to those observed in AmFm stars in open clusters except that they are larger by a factor of about 3. To reduce the calculated anomalies to the observed ones, an additional source of turbulence (or some other hydrodynamical process) must be introduced. The mixed zone must extend about 5 times deeper than the iron convection zone. Detailed comparisons to a few AmFm stars have been carried out.The LiBeB abundances observed in clusters give additional information. The abundances of the 28 species offer considerable constraints on the models. Various potential turbulence models have been introduced in a stellar evolution code and results of evolutionary calculations for Li gap stars are discussed in the light of the constraints offered by the abundances of LiBeB and metals. The radiative accelerations of LiBeB have also been recalculated taking the effect of changing metal abundances into account. This modifies the expected Li gap in the absence of turbulence.