Corner plot of the χ² surface as a function of the model parameters for VLA 12N. The region size has been fixed externally for these fits. We show an individual corner plot for ℓ_⊥ = 100 AU, the best-fit source size. The violet contours correspond to the minimum χ² value. Top panels in each column: probability density distributions for the marginalised parameters; confidence intervals (±1σ) are shown as violet shaded rectangular regions, and the maximum-likelihood estimate is shown by a vertical dashed line. These values together with the upper and lower uncertainties inferred from the confidence intervals are also reported.