Abstract We present high-precision, multi-band CCD photometry of two less-studied close binaries V1123 Tau and V1128 Tau. Complete covered light curves and a number of new times of light minima of the two eclipsing systems were obtained, based on which, revised orbital elements and new ephemerides were given. By adopting the Wilson-Devinney method, the light curves were analyzed. The photometric solutions confirm the W UMa-type nature of the binary systems. With the less-massive secondary slightly cooler than the primary, V1123 Tau could be classified as an A-type contact system. While V1128 Tau is typically considered a W-type W UMa star, the surface temperature of its secondary component is determined to be absolutely higher than the primary by about 270 K. Combining with the results of radial-velocity solutions, we determined absolute parameters of the two systems. The mass, radius and luminosity for each component of V1123 Tau were derived as: 1.36 ± 0.05M⊙ , 1.37 ± 0.02R⊙ , and 2.01 ± 0.07L⊙ and 0.40 ± 0.02M⊙ , 0.80 ± 0.01R⊙ , and 0.67 ± 0.04L⊙ , respectively. For V1128 Tau, the absolute parameters were computed to be 1.09 ± 0.03M⊙, 1.01 ± 0.01R⊙, and 1.34 ± 0.06L⊙ and 0.58 ± 0.01M⊙, 0.76 ± 0.01R⊙, and 0.91 ± 0.05L⊙, respectively. Based on these results, the evolutionary status and the physical nature of the two binary systems are discussed, while also connecting with the theoretical models.

Keywords binaries: eclipsing — stars: late-type — stars: activity — stars: individ- ual (V1123 Tau, V1128 Tau)

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