Interferometric Survey of Stellar Parameters: Mass of the metallic A-type binary β Aur

Abstract

Long-baseline optical interferometry provides spatially resolved observations of close binaries, complementing spectroscopic and photometric constraints on stellar parameters. With the capabilities of the new visible CHARA/SPICA instrument and the multiple spectral band operation of CHARA, our goal is to resolve orbits of short-period binaries and develop a robust framework for combining interferometric, spectroscopic, and photometric observations into a single consistent model. For our target sample, we selected suitable binaries based on brightness, angular separation, and orbital properties based on the expected performance of the CHARA/SPICA instrument. As a case study, we analysed the bright eclipsing binary β Aurigae, composed of two slightly evolved A1 stars. We combined new interferometric observations of code to simultaneously fit all observables using MCMC sampling. We performed a detailed analysis of the noise statistics of each data set and in the end we adopted a profile likelihood approach to account for underestimated noise and systematics. obtained with CHARA/SPICA, MIRC--X, and MYSTIC with archival MIRC data, radial velocities, and light curves. We first derived astrometric positions from interferometric observables and computed an orbital solution. Afterwards, we implemented a unified model, capable of tying interferometric modelling with the ellc We derived a consistent orbital and physical solution for through joint modelling. The inclusion of interferometric data tightly constrains the angular semi-major axis and inclination. Using profile likelihood to account for the different intrinsic levels of uncertainty of the fundamentally different observables, we derived the masses of the two stars, M_1 = 2.359 ± 0.005, and M_2 = 2.293 ± 0.004, their radii R_1 = 2.752 ± 0.002,̊sun and R_2 = 2.622 ± 0.002,̊sun, and the distance to the binary, d = 24.30