Fourier transforms of the original SC light curve and of the light curve pre-whitened for 2, 9, 46, and 63 frequencies. The blue dashed lines denote the 4 ⟨ A ⟩ significance level, where ⟨ A ⟩ is calculated as the moving average of radius 8 d^-1 of the pre-whitened spectrum. The frequency gap between ≈15 and 27 d^-1 is indicated with a grey band. The vertical dotted line denotes the Nyquist limit of the LC data.