Absolute dimensions of detached eclipsing binaries – I. The metallic‐lined system WW Aurigae

WWAurigae is a detached eclipsing binary composed of two metallic-lined A-type stars orbiting each other every 2.5 days. We have determined the masses and radii of both components to accuracies of 0.4% and 0.6%, respectively. From a cross-correlation analysis of high-resolution spectra we find masses of 1.964±0.007M⊙ for the primary star and 1.814±0.007M⊙ for the secondary star. From an analysis of photoelectric uvby and UBV light curves we find the radii of the stars to be 1.927±0.011R⊙ and 1.841± 0.011R⊙, where the uncertainties have been calculated using a Monte Carlo algorithm. Fundamental effective temperatures of the two stars have been derived, using the Hipparcos parallax of WWAur and published ultraviolet, optical and infrared fluxes, and are 7960±420 and 7670±410K. The masses, radii and effective temperatures of WWAur are only matched by theoretical evolutionary models for a fractional initial metal abundance, Z, of approximately 0.06 and an age of roughly 90Myr. This seems to be the highest metal abundance inferred for a well-studied detached eclipsing binary, but we find no evidence that it is related to the metallic-lined nature of the stars. The circular orbit of WWAur is in conflict with the circularization timescales of both the Tassoul and the Zahn tidal theories and we suggest that this is due to pre-mainsequence evolution or the presence of a circular orbit when the stars were formed.