Power spectrum of the observed microlensing light curve computed as the mean of the power spectra obtained for 1000 different realisations of photometric noise for every value of η sampling the range [30:100] days with steps of 5 days used for the spline fitting parameter (see text). The 1−σ envelope is given by the standard deviation of the same set of power spectra. The dashed black line marks the boundary between low and high frequency and the grey area indicates our adopted frequency limit of 10⁻² days⁻¹, below which photometric uncertainties dominate the data.