NILC residuals for SO-SAT dataset with the d1s1 Galactic model. On the left: Mean angular power spectra of NILC foregrounds (solid) and noise (dashed) residuals over 200 simulations. On the right: Posterior distributions of an effective tensor-to-scalar ratio fitted to the foregrounds residuals in the case of half de-lensing (A_L = 0.5). Both for the plots of the angular power spectra and the estimation of the posterior a binning scheme of Δℓ = 15 has been used. On the top: Results when E–B leakage is corrected with the recycling method (r-NILC). On the bottom: Results when the ZB- (blue) and hybrid ZB-NILC (red) methods are applied. Everywhere the grey region represents the primordial tensor BB angular power spectrum for r ∈ [0.003, 0.01]. The lower bound represents the targeted upper limit at 68% CL by SO in case of no detection, the upper one the targeted detection at few σ significance. The spectra have been estimated masking the regions most contaminated by foregrounds for a final f_sky of 8%.