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Department 1



Context. V1094 Tau is a bright eclipsing binary star with an orbital period close to nine days that contains two stars similar to the Sun.

Aims. Our aim is to test models of Sun-like stars using precise and accurate mass and radius measurements for both stars in V1094 Tau.

Methods. We present new spectroscopy of V1094 Tau, which we use to estimate the effective temperatures of both stars and to refine their spectroscopic orbits. We also present new, high-quality photometry covering both eclipses of V1094 Tau in the Strömgren uvby system and in the Johnson V-band.

Results. The masses, radii, and effective temperatures of the stars in V1094 Tau are found to be MA = 1.0965 ± 0.0040 M, RA= 1.4109 ± 0.0058 R, Teff,A = 5850 ± 100 K, MB = 1.0120 ± 0.0028 M, RB = 1.1063 ± 0.0066 R, and Teff,B = 5700 ± 100 K. An analysis of the times of mid-eclipse and the radial velocity data reveals apsidal motion with a period of 14 500 ± 3700 years.

Conclusions. The observed masses, radii, and effective temperatures are consistent with stellar models for an age ≈6 Gyr if the stars are assumed to have a metallicity similar to the Sun. This estimate is in reasonable agreement with our estimate of the metallicity derived using Strömgren photometry and treating the binary as a single star ([ Fe/H ] = −0.09 ± 0.11). The rotation velocities of the stars suggest that V1094 Tau is close to the limit at which tidal interactions between the stars force them to rotate pseudo-synchronously with the orbital motion.



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