Characterization of the Kepler targets. Top-left: distribution of apparent Gaia G-band magnitudes. The targets are mostly concentrated in the 10 < G < 16 mag range. Top-right: distribution of Gaia distances. The distribution peaks around ~1 kpc. Bottom-left: distribution of RUWE values, with the vertical lines indicating RUWE = 1.0 (green), 1.2 (cyan), and 1.4 (red). From this, RUWE binaries are later identified in Sect. 4. Bottom-right: distribution of calibrated metallicity values, for the subsample with best-quality gspspec data. The distribution peaks around [M/H] = 0 dex, in agreement with the literature.