1994A&A...291..777N

Improved radii, masses and temperatures of the evolved early A-type binary β Aurigae are determined through an analysis of the available light and radial velocity curves. A new spectroscopic determination of the luminosity ratio is used to constrain the ratio of the radii, k=r_B/r_A, which is indeterminate from the photometric light curves; we find k=0.95±0.015. The resulting physical parameters of the two stars, accurate to ∼1%, are: masses: M_A=2.38M_☉, M_B=2.31M_☉; radii: R_A=2.77R_☉, R_B=2.63R_☉; logg_A=3.93, logg_B=3.96; effective temperatures: T_A=9350K, T_B=9200K. β Aur has thus evolved into the upper part of the main-sequence band. Our measured rotational velocities of 33 and 34 km/s for the two components correspond exactly to synchronous rotation in the circular orbit. Comparison with new stellar evolution models gives a very good fit at an age of 5.710⁸yr and indicates that β Aur has a metal abundance that is close to solar or slightly below. β Aur is yet another system which is considerably younger than the Sun, but no richer in heavy elements. Recent optical interferometry of β Aur yields an accurate distance to the system (24.8±0.8pc) and allows an interesting cross-check of four different distance estimators. The result is a tighter constraint on the effective temperatures, rather than the masses and radii of the components.