Lomb–Scargle periodograms of the X-ray light curves computed from the simulations. Left: LS periodogram of the X-ray light curve produced by the near-horizon flow around the IMBH as calculated from an ADAF model. The highest peak is at ∼210 years, while other prominent peaks are at ∼54 and ∼83 years. The dotted horizontal lines mark inferred confidence levels based on 10 000 bootstrap realizations. Right: LS periodogram of the total X-ray luminosity exhibits the highest peak at ∼104 years. Other prominent peaks are at ∼202, ∼271, ∼55, and ∼74 years. The dotted horizontal lines stand for the confidence levels, as in the left panel.