GLS power spectrum for the GJ 253 data, based on NZP-corrected SERVAL RVs, DRS RVs, and stellar activity indicators from DRS and SERVAL as labeled in the panels. The horizontal lines in the GLS periodograms show FAP levels of 10%, 1%, and 0.1%. Blue vertical lines indicate the orbital period of GJ 253 b and c. The magenta vertical line indicates the periodicity near 36 d, which is present in DRS FWHM, BIS-span, contrast, and the SERVAL dLW activity indicators that are likely related to the stellar rotational period.