Reconstructed power spectra of the giant flare of SGR 1806-20: For Figure 3a and Figure 3c we used smoothness-enforcing priors with σ_sm = 5 × 10⁵ and σ_sm = 10⁵, respectively. The uncertainty intervals are given as grey shaded areas. In Figure 3b we show the reconstructed power spectrum again from the data themselves as in Figure 3a, along with the power spectrum of the logarithmic reconstructed light curve of Fig. 1a. Because of the high resolution of the reconstructed power spectra, only every fourth point of the regular grid is plotted. Each pixel has a volume of 1∕655 Hz.