Analysis of the PSD of the Kepler/K2 (left) and TESS (right) LCs. In each panel, the black solid line shows the PSD of the LC after masking the planetary transits. The two vertical dashed lines mark the frequencies 0.35 d⁻¹ and 0.70 d⁻¹. The confidence band in orange shows the average periodogram obtained using the rotation GP, as discussed in the text. Similarly, the blue confidence band corresponds to the GP model used in this work.