Posterior shell parameter distributions for the model with a linear (left) and Gaussian (right) radial intensity profile. Top panels, shell size; center panels, radial intensity parameters (slope, R_sl, at left; peak position, ρ_peak, at right); bottom panels, R_i/R_o. The color codes are the same as in the previous figures. Dotted lines in the top panels show the power law expansion model R_o ∝ t^m (with m = 0.8). Dotted (dashed) lines in the center and bottom panels mark the average (±1σ) values for the whole campaign.