χ² value as a function of the time delay in the observer’s frame for the Mg II line emission (magenta line) as well as for the Fe II line emission (blue line). The global χ² minima for each line are depicted by the vertical dashed lines. The χ² time-delay dependence for the previous, shorter continuum-Mg II light curves (Czerny et al. 2019) is shown as a gray line with the global minimum at the time delay twice as large as for the current data. Cont:79, 113 and line:26, 35 represents the number of observations.