Results from the photometric flux variability analysis. Top: Optical SED of Fairall 9 derived from the mean fluxes in the u, v, b, y, and I filters. Middle: Differential SED constructed from the difference between the maximum and minimum fluxes in the corresponding filters. Bottom: Normalized excess variance, F_var, as a function of wavelength. In both the top and middle panels, the dot-dashed teal line represents the best-fit power law with a free spectral index, while the dashed brown line corresponds to a power law with the index fixed at −4/3, as predicted by the standard thin accretion disk model. The orange-shaded regions indicate the ±1σ range, representing the wavelength uncertainty of each filter, as quantified by the rms width of its transmission curve.