Pre-whitening sequence of detected pulsation modes. Top panel: Lomb-Scargle Periodogram of the TESS time series in the relevant 270−420 μHz frequency range. The horizontal dotted line indicates four times the median noise level and corresponds to the chosen detection limit. Middle panel: residual periodogram after pre-whitening the four dominant peaks identified in the top panel. Two additional low-amplitude peaks are identified. Bottom panel: from top to bottom are the original, reconstructed (from the frequencies, amplitudes, and phases of the six fitted sine waves; plotted upside down) and residual periodograms after completing the pre-whitening process.