Generalised Lomb-Scargle periodogram of the longitudinal field near-infrared time series, from top to bottom EV Lac, DS Leo, and CN Leo. In each panel the rotation period corresponding to the highest peak is highlighted with a green dotted line, while two FAP levels (0.1% and 0.01%) are shown as grey horizontal lines. The window function of the entire time series is included and mirrored with respect to the x-axis (VanderPlas 2018) to highlight aliases due to the observation cadence and scheduling.