Clustering periodogram analysis (Kemmer et al. 2025) for the activity indices of GJ 3512 (top) and GJ 9773 (bottom). The 0.1% FAP threshold is shown as a horizontal dotted grey line, while vertical dashed lines mark the position of common periods caused by the sampling of data and their harmonics as labelled. Symbols with different colours correspond to clusters of periods that appear on different activity indicators. The mean values are reported in the legend.