Posterior probability distribution on the source size and flux density in our EVN 4.9 GHz epochs at T − T₀ = 43 (RG1013 C, left), 117 (RG013 D, centre) and 261 (RG013 F, right) days. In each corner plot, the top-left and bottom-right sub-panels show histograms of the posterior samples of F_ν and FWHM, with the vertical solid lines showing the median and the vertical dashed lines bracketing the 68% credible interval or, if the latter extends to 0, the 95% credible upper limit. The bottom-left sub-panel of each corner plot shows the smallest contours containing 68% and 95% of the posterior probability.