Fundamental parameters for dEB SB2 binary system J064726.39+223431.6

We present a study of eclipsing binary J064726.39+223431.6 using spectra from the LAMOST-MRS and TESS photometry. We use full-spectrum fitting to derive radial velocities and spectral parameters: ${T_{\mathrm{e}\mathrm{f}\mathrm{f}}}_{A,B}=6177,5820$ K, $v\sin i_{A,B}=59,50\text{kms}$ and ${[\mathrm{F}\mathrm{e}\mathrm{/}\mathrm{H}]}_{A,B}=-0.19$ dex. The orbital solution and light curve analysis suggest that it is a close pair of fast rotating stars on circular orbit. We measure their masses to be $M_{A,B}=1.307\pm 0.007,1.129\pm 0.005M_{\odot }$ and their radii to be $R_{A,B}=1.405\pm 0.052,1.219\pm 0.060R_{\odot }$ resulting in surface gravities of $\log g_{A,B}=4.259\pm 0.033,4.319\pm 0.042$ (cgs). Theoretical models cannot match all of these properties, predicting significantly higher $T_{\mathrm{e}\mathrm{f}\mathrm{f}}$ for a given metallicity. Derived age of the system 1.56 Gyr indicates that both components are younger than Sun, which contradicts to much longer orbit’s circularisation timescale.