Radial velocity residuals (“Observed minus Calculated” or O–C for short) of the best-fitting model to all BEBOP binaries forall 1519 observations, stacked on top of each other as a function of the scaled radial velocity value δ, defined according to Eq. (7). The δ value says how far the observed radial velocity observation was from the systemic velocity, scaled by the average FWHM for that target. The two roughly horizontal dark blue lines are the root mean squared (RMS) values of the residuals, split into positive and negative values. If the RMS were maximised near δ = 0 then this would be indicative of wide-spread spectral contamination from the secondary star, but this is evidently not the case.