Top panels: spurious estimated RVs (black dots) caused by a facula in the simulated data using a Normal and a SN model, the estimated RVs using Eq. (5) (red pluses), and the estimated RVs using the usual correction for stellar activity (green triangles), based on RV_activity = β₀ + β₁γ + β₂SN FWHM for the SN fitand on RV_activity = β₀ + β₁BIS SPAN + β₂FWHM for the Normal fit. Bottom panels: residuals from the model fit using Eq. (5) (red pluses) and the residuals from the usual correction (green triangles). The standard deviations are also reported in the legend, and the residuals have a smaller systematic component when using the proposed model of Eq. (5) compared to the usual model. The tests of statistical significance on the parameters are presented in Table 2.