The Evolution of Procyon A

Abstract

A grid of stellar evolution models for Procyon A has been calculated. These models include the best physics available to us (including the latest opacities and equation of state) and are based on the revised astrometric mass of Girard et al. (1996). The long standing discrepancy between the evolutionary mass and the astrometric mass is now resolved, a result of the newly determined astrometric mass. Models were calculated with helium diffusion and with the combined effects of helium and heavy element diffusion. Oscillation frequencies for $\ell=0,1,2$ and 3 $p$-modes (and $g$-modes) were calculated for these models. The predicted $p$-mode frequencies are relatively unaffected by heavy element diffusion and convective core overshoot. The inclusion of a modest stellar wind which effectively suppresses the helium diffusion in the surface layers has a modest effect on the $p$-mode frequencies. The evolutionary state (main sequence or shell hydrogen burning) of Procyon A has the largest effect on the predicted $p$-mode frequencies. The $g$-modes show a greater sensitivity to the various model parameters.