Periodograms of the likely extragalactic source eRASSt J055033.4-663653, whose light curve is shown in Fig. 9. The periodograms of individual segments of the light curve are shown in light blue. The averaged periodogram is displayed in dark blue. The red line denotes the best fit to all the periodograms of segments of the light curve, using an aliased single power law with α = 1.093 ± 0.050. The figure also features a dashed pink line that depicts a pink noise trend.