Projected regions inside the cloud observed simultaneously at time 320 yr by flares of different durations T (where the black region corresponds to illumination by an instantaneous flare). In the case of the three clumps considered in Fig. 14, the minimum flare duration required for both the furthest apart clumps (shown with solid red lines in the plot) to be visible to the observer at the same time is T ~ 40 yr. In the case in which both substructures are visible simultaneously in the reflected X-ray intensity maps, one can infer that the source’s flare must have lasted at least T ~ 40 yr.