Fourier transform of TESS light curve of Ross 548. Left panels: sub-Nyquist frequency range where the signal exceeds the 0.1% FAP (S/N = 4.54, horizontal dashed line). The peaks correspond to f₃ and f₄ from Table 3 (red lines), and the aliases (reflected across the Nyquist frequency) of f₁ and f₂ (blue vertical lines). Right-hand panels: transform above the Nyquist frequency, where the real periodicity – alias situation is reversed. Two bottom panels: residuals in the spectrum after pre-whitening by the least-squares fit sinusoids f₁, f₂, f₃, f₄ listed in Table 4.