The Evolution of AmFm Stars, Abundance Anomalies, and Turbulent Transport

Abstract

Stellar evolution models of stars of 1.45 to 3.0 M fi have been calculated including the atomic diffusion of metals and radiative accelerations for all species in the OPAL opacities. As the abundances change, the opacities and radiative accelerations are continuously recalculated during evolution. These models develop iron peak convection zones centered at a temperature of approximately 200 000 K. If one then assumes that there is sufficient overshoot to homogenize the surface regions between the hydrogen, helium and iron peak convection zones, it is shown here that the surface abundances variations that are produced, without any arbitrary parameter, closely resemble the abundance anomalies of AmFm stars except that they are larger by a factor of about 3. Detailed evolutionary model calculations have been carried out varying the turbulence in the outer stellar regions in order to improve the agreement with the observed anomalies in AmFm stars. The outer mass mixed by turbule...