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

• Published in: The Astrophysical journal 2018-09, Vol.864 (1), p.99
• Main Authors: Joyce, M., Chaboyer, B.
• Format: Article
• Language: English
• Subjects: Astronomical models; Astrophysics; Binary stars; Constraint modelling; Convective mixing; Luminosity; Mixing length; Physics; Seismic activity; Stellar evolution; Stellar models; Stellar seismology; Stellar systems
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aad464

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 3 σ . 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.