Microlensing model used to reproduce the observed index time series. From left to right: μ^cont, μ^BLR, WCI, and RBI. Top panels: Rebinned time series of the four observed indices computed from the spectra of images A and D obtained at the same epoch. The solid lines denote the reconstructed time series. Bottom panels: tracks (solid lines) sampled from two different regions that reproduce the indices in the top panels. In that example, the BLR model is characterized as KD, i = 22°, q = 1.5, r_in = 0.5 r_E, r_s = 0.1 r_E. The bottom panels present only two out of many regions on a much wider map. The units of the tracks are converted to r_E for v_⊥ = 500 km s⁻¹.