Time-frequency diagrams of the decorrelated photometry of HD 149 404, averaged over the spacecraft orbit before (upper panels) and after (lower panels) pre-whitening for P_orb and P_orb/2. Left panels: evolution of the Fourier periodogram as a function of the heliocentric Julian day at the middle of the 20-day sliding window (see text). Dark blue, light blue, and cyan stand respectively for semi-amplitudes ≥9 mmag, ≥6 mmag, and ≥3 mmag. Right panels: Fourier periodograms over the full duration of the BRITE campaign.