2023MNRAS.519.5454K

We present a study of the detached eclipsing binary J064726.39 + 223431.6 using spectra from the LAMOST medium-resolution spectra and Transiting Exoplanet Survey Satellite photometry. We use full-spectrum fitting to derive radial velocities and spectral parameters: ${T_{\rm eff}}_{A,B}=6177,\, 5820$ K, $V \sin {i}_{A,B}=59,\, 50~\, {\rm km}\, {\rm s}^{-1}$, and [Fe/H]_A,B = -0.19 dex. The orbital solution and light-curve analysis suggest that it is a close pair of fast rotating stars on a circular orbit. We measure their masses to be $M_{A,B}=1.307\pm 0.007,\, 1.129\pm 0.005\, \mathrm{M}_\odot$ and their radii to be $R_{A,B}=1.405\pm 0.052,\, 1.219\pm 0.060\, \mathrm{R}_\odot$, resulting in surface gravities of $\log {\rm (g)}_{A,B}=4.259\pm 0.033,\, 4.319\pm 0.042$ (cgs). Theoretical models cannot match all of these properties, predicting significantly higher T_eff for a given metallicity. The derived age of the system is 1.56 Gyr, which indicates that both components are younger than Sun, which contradicts to much longer orbit's circularization time-scale.