Variance– and slope–frequency plots of our AGN sample. Upper panel: observed VFP of a 10⁸ M_⊙ AGN as a function of the rest-frame frequency ν_T using our measurements from Table 1 (filled symbols). The red empty symbols indicate the best-fit model values (α(T_max) in Eq. (4)). For reference, we also show the theoretically expected trends for a 10⁸ M_⊙ BH monitored with an average Δt_min = 250 s (dashed line) and Δt_min = 300 days (dotted line), but we stress that the comparison should be made between the filled and empty points. Lower panel: measured and best-fit model slope of the –M_BH relations (β(T_max) in Eq. (4)); symbols have the same meaning as those in the upper panel.