* Astronomy

Title: A Turnoff Detached Binary Star V568 Lyr in the Kepler Field of the Oldest Open Cluster (NGC 6791) in the Galaxy
Author: K. Yakut, P. P. Eggleton, B. Kalomeni, C. A. Tout, J. J. Eldridge

We present the Kepler photometric light-variation analysis of the late-type double-lined binary system V568 Lyr that is in the field of the high metallicity old open cluster NGC 6791. The radial velocity and the high-quality short-cadence light curve of the system are analysed simultaneously. The masses, radii and luminosities of the component stars are M1=1.0886±0.0031 Solar masses, M2=0.8292±0.0026 Solar masses, R1=1.4203±0.0058 Solar radii, R2=0.7997±0.0015 Solar radii, L1=1.85±0.15 Solar luminosity, L2=0.292±0.018 Solar luminosity and their separation is a=31.060±0.002 Solar radii. The distance to NGC 6791 is determined to be 4.260±0.290kpc by analysis of this binary system. We fit the components of this well-detached binary system with evolution models made with the Cambridge STARS and TWIN codes to test low-mass binary star evolution. We find a good fit with a metallicity of Z=0.04 and an age of 7.704Gyr. The standard tidal dissipation, included in TWIN is insufficient to arrive at the observed circular orbit unless it formed rather circular to begin with.

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