We present observations and analysis of an RS CVn-type double-lined eclipsing binary system, RU Cnc. The system has been observed for over a century. The high-quality long-cadence \emph{ Kepler} K2 C5 and C18, newly obtained observations, and two radial velocity curves were combined and analyzed simultaneously assuming multi-spot model. The masses, radii and luminosities of the component stars are precisely obtained as $M_\textrm{ c} = 1.386\pm0.044\, M_{ _\odot}$, $M_\textrm{ h} = 1.437 \pm 0.046\, M{ _\odot}$, $R_\textrm{ h} = 2.39\pm 0.07\, R{ _\odot}$, $R_\textrm{ c} = 5.02 \pm 0.08\, R{ _\odot}$, $L_\textrm{ h} = 11.4\pm 1.2\, L{ _\odot}$, $L_\textrm{ c} = 12.0 \pm 1.0\, L{ _\odot}$ and with a separation of $\textrm{ a} = 27.914 \pm 0.016\, R{ _\odot}$. The distance of the system is determined to be $380\pm 57\,$ pc which is consistent with the Gaia DR2 result. Long-term detailed period variation analysis of the system indicate a period decrease of $7.9\times10^{ -7}$ days per year. The results suggest the cooler component to be on the red giant branch (RGB) and the hotter one to be still on the main sequence.
Categories: astro-ph.SR