The Nature of the Eccentric Double-lined Eclipsing Binary System KIC 2306740 with Kepler Space Photometry

We present a detailed study of KIC 2306740, an eccentric double-lined eclipsing binary system. Kepler satellite data were combined with spectroscopic data obtained with the 4.2 m William Herschel Telescope (WHT). This allowed us to determine precise orbital and physical parameters of this relatively long period (P = 10.ͩ3) and slightly eccentric (e = 0.3) binary system. The physical parameters have been determined to be M ₁ = 1.194 ± 0.008 M _⊙, M ₂ = 1.078 ± 0.007 M _⊙, R ₁ = 1.682 ± 0.004 R _⊙, R ₂ = 1.226 ± 0.005 R _⊙, L ₁ = 2.8 ± 0.4 L _⊙, L ₂ = 1.8 ± 0.2 L _⊙, and orbital separation a = 26.20 ± 0.04 R _⊙ through simultaneous solutions of the Kepler light curves and WHT radial velocity data. Binarity effects were extracted from the light curve in order to study intrinsic variations in the residuals. Five significant and more than 100 combination frequencies were detected. We modeled the binary system assuming nonconservative evolution models with the Cambridge stars (twin) code, and we show the evolutionary tracks of the components in the $logL\text{--}logT$ plane, the $logR\text{--}logM$ plane, and the $logP\text{--}age$ plane for both spin and orbital periods together with eccentricity e and $log{R}_1$. The model of the nonconservative processes in the code led the system to evolve to the observed system parameters in roughly 5.1 Gyr.