Joint likelihood contours (95.6% and 68.7%) for couples of best-fit parameters for the experimental configuration EC4 (6-band cryogenic photometer operating in L2) where the data are analysed by fitting four parameters (τ_t, T_e, ΔI_d, ΔT_CMB). The filled contours are for a Gaussian prior on T_e with σ = 3   keV; the dashed contours are for a Gaussian prior with σ = 8   keV. The * symbols mark the input values of parameters.