Periodograms of CHEOPS and TESS lightcurves. Left: Periodogram of the first CHEOPS visit prewhitened by the significant oscillations (black), and averaged periodogram combining two one-day subseries (red). Right: Periodogram of TESS sector 29 prewhitened by the significant oscillations (black), and averaged periodogram combining the 25 available one-day subseries (red). In both panels, best-fitting models resulting from Harvey function fits given by Eq. (4) are shown in yellow. The cut-off frequencies of the flicker noise resulting from the MCMC analyses are indicated by the blue vertical dashed lines. We note the different frequency ranges on the x-axes.