Frequency-averaged TE and EE spectra (without fitting for temperature-to-polarization leakage). The theoretical TE and EE spectra plotted in the upper panel of each plot are computed from the Planck TT+lowP best-fit model of Fig. 1. Residuals with respect to this theoretical model are shown in the lower panel in each plot. The error bars show ± 1σ errors. The green lines in the lower panels show the best-fit temperature-to-polarization leakage model of Eqs. (11a)and (11b), fitted separately to the TE and EE spectra.