Corner plots of the MCMC chain results and bar plots of selected orders for 100 noise realizations for case 1. The left panels show corner plots of the time shift and differential dust extinction retrieved from 100 noise realizations for case 1. We plot the contours for the 1σ (68%, solid red line) and 2σ (95%, dashed red line) credible intervals for the differential dust extinction A_V, B − A_V, A and the time delay Δt. The input values in light blue are Δt = 16.3 days and A_V, B − A_V, A = 0.2 mag. On the right, we show histograms of the selected orthogonal polynomial orders of fitting using the BIC for the corresponding cases on the left. Panel a: Case 1 with one color curve u − g. Panel b: Orders of fitting selected for case 1 with one color curve u − g. Panel c: Case 1 with two color curves u − g and u − r. Panel d: Orders of fitting selected for case 1 with two color curves u − g and u − r. We impose the same order for both color curves.