2022MNRAS.511.2285W

Spotted detached eclipsing binaries (DEBs) offer insights into starspots on binaries. In this work, we study three spotted DEBs, KIC 8097825, KIC 6859813 and KIC 5527172, which have been observed using Kepler photometry and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) spectroscopy. The physical parameters of binaries are determined by binary modelling. The size, lifetime and single/-double-dip ratio (SDR) of starspots are derived by starspot analysis. KIC 8097825 has large starspots. KIC 6859813 has a spot rotation period shorter than its orbital period but the system should be synchronized by inference from time-scale estimation. The difference may be the result of the surface differential rotation. KIC 5527172 has a long spot lifetime and an M-dwarf component with an inflation radius. The primaries of these binaries and the secondary of KIC 8097825 have spots. Adding spotted DEBs from the literature, we compare the starspots on binaries with those on the single stars. The spot sizes of starspots on 65 per cent of binaries are smaller than the median of those on single stars. The lifetimes of starspots on binaries are consistent with those on single stars when the rotation periods are larger than 3 d. SDRs for half of the binaries are consistent with those of single-star systems, while the other half are smaller. The relative lifetime positively correlates with the rms and SDR but negatively correlates with the rotation period. These relations are similar to those of spots on single-star systems. Binaries with luminosity ratios close to the unit tend to have more double dips.