Generalized Lomb-Scargle periodogram of the 2019 HARPS measurements (upper panel) and RV residuals, following the subtraction of the Doppler signals of planet b (second panel), planets b and c (third panel), and planets b and c plus the 20.5 d signal (fourth panel). The periodogram of the Ca II H & K lines activity indicator log , of the CCF BIS and FWHM, and of the window function are shown in the last four panels. The horizontal dashed lines mark the 0.1% FAP. The orbital frequencies of planets b, c, and d, as well as the stellar rotation frequency and its first harmonic are marked with vertical dashed lines.