Periodograms of the detrended light curve segments t₁ (pre-dip, toppanel) and t₃ (post-dip, bottom panel) computed from the respective MOS1 (black) and MOS2 (orange) data. Vertical blue dotted lines represent the detected frequencies f₂ = 0.35 mHz and f₃ = 0.92 mHz with its first harmonics 2 × f₃ ~ 1.84 mHz (see Table 4). Horizontal blue lines represent the 90, 99, and 99.9% confidence levels.