GLS periodograms of the RV data of GJ 3942. The contents of the panels are a) the periodogram of the RV data; b) residuals after correcting for a 16.3-day signal; c) residuals after subtracting simultaneously 16.3- and 6.9-day signals; and d) residuals after simultaneously correcting for signals at 16.3, 6.9, and 10.4 days. For each panel, we give the analytical FAP of the respective model (in red if FAP < 0.1%). Yellow bands indicate the periods at 16.3, 10.4, and 6.9 days. The green lines show the first and second harmonics of the 16.3-day signal, namely 8.2 and 5.4 days. Blue horizontal lines show the 1% (dashed) and 0.1% (solid) FAP levels (from bootstrapping) of the respective dataset. Additionally, we show in the upper parts of each periodogram the WF in gray after being flipped, scaled, mirrored, and period-shifted to the main peak of the respective dataset.