Density plot of the relation between r_ipd, G and of the small-separation binary model fit to the G-band photometry (Eq. 5). A low together with a high r_ipd, G suggests a strong scan-angle-dependent signal, while a low in combination with a low correlation usually corresponds to non-variable (constant) stars with an insignificant amplitude, as seen (and expected) for the majority of the GAPS data set. As a guide for low values, we added horizontal lines at thresholds 3 (short-dashed) and 9 (longer-dashed; see Sect. 6.4 for a more detailed discussion, and see also Fig. A.4 for the significance of the fitted amplitude). Plots for N_3band ≥ 20 and N_noEpsl, G ≥ 20.