Classically and Asteroseismically Constrained 1D Stellar Evolution Models of α Centauri A and B Using Empirical Mixing Length Calibrations

Abstract

Abstract The bright, nearby binary α Centauri provides an excellent laboratory for testing stellar evolution models, because it is one of the few stellar systems for which we have high-precision classical (mass, radius, luminosity) and asteroseismic (p-mode) observations. Stellar models are created and fit to the classical and seismic observations of both stars by allowing for the free variation of the convective mixing length parameter α MLT. This system is modeled using five different sets of assumptions about the physics governing the stellar models. There are 31 pairs of tracks (out of ∼150,000 generated) that fit the classical, binary, and seismic observational constraints of the system within 3σ. Models with each tested choice of input physics are found to be viable, but the optimal mixing lengths for α Cen A and α Cen B remain the same regardless of the physical prescription. The optimal mixing lengths are α MLT,A/α ⊙ = 0.932 and α MLT,B/α ⊙ = 1.095. That α Cen A and α Cen B require subsolar and supersolar mixing lengths, respectively, to fit the observations is a trend consistent with recent findings, such as those of Kervella et al., Joyce & Chaboyer, and Viani et al. The optimal models find an age for α Centauri of 5.3 ± 0.3 Gyr.