Time delay (ICCF centroid) as a function of pivot wavelength of the filters. The horizontal error bars represent the rms width of the filters. The best-fit model is shown by the dashed magenta line, while the fit fixing ﹩\beta =4/3﹩ is shown by the dotted magenta line. Predictions for a thin-disk model with ﹩{\dot{m}}_{{\rm{E}}}=L/{L}_{{\rm{Edd}}}﹩ are shown by the solid cyan lines, although the assumptions of the model are unlikely to hold at large ﹩{\dot{m}}_{{\rm{E}}}﹩ (see Section 5.3). The mean lag of the He II λλ1640, 4686 lines is shown by the horizontal dashed black line (Paper I; Paper V).