Top panel: variation of the GLS periodogram of the light curve of AB Dor, split into parts containingfive rotations each. We note that the reduced error sizes in the time range between 1500 ≲ TJD ≲ 1550 are related to the shape of the light curve during that time (which is closer to sinusoidal than the rest of the light curve) and the GLS periodogram’s ability to measure the periods of sinusoidal-like signals more accurately. Bottom panel: mean peak-to-peak variation amplitude assuming sets of five rotations (the y-axis is in normalized flux units).