Fundamental parameters for double-lined spectroscopic and detached eclipsing binary system J064726.39+223431.6.


 We present a study of the detached eclipsing binary J064726.39+223431.6 using spectra from the LAMOST medium-resolution spectra and TESS photometry. We use full-spectrum fitting to derive radial velocities and spectral parameters: TeffA, B = 6177, 5820 K, Vsin iA, B = 59, 50  km 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 MA, B = 1.307 ± 0.007, 1.129 ± 0.005 M⊙ and their radii to be RA, B = 1.405 ± 0.052, 1.219 ± 0.060 R⊙ resulting in surface gravities of log (g)A, B = 4.259 ± 0.033, 4.319 ± 0.042 (cgs). Theoretical models cannot match all of these properties, predicting significantly higher Teff 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 circularisation timescale.