Fourier periodogram of TESS photometry of HD 192639 during the different sectors. The left-hand panels display the periodogram between 0 and 5 d^–1 clearly unveiling the red-noise behaviour. The bestfit red-noise relation is shown in red. The right-hand panels provide a zoomed-in view of the region below 1 d^–1. The dashed blue vertical line yields the ν₁ frequency previously found in spectroscopic time series by Rauw et al. (2001).