Residual BB power spectra for the frequency band centered at 140 GHz. The thick blue lines are the fiducial (CMB) (lensing BB, r = 0). The dashed-dotted lines show the residual spectra obtained as the average over ten Gaussian error realizations of the perturbations applied to each systematic parameter. Different colors correspond to different values of the variance σ_Δx of the error realizations applied to the parameter x. The dotted line is the noise bias , as described in Sect. 5.4.