Shape periodograms for δ Cep. Rows correspond to: CCF profiles, their Gaussian fits, median-residual CCFs, Gaussian-residual CCFs, and normalised spectra. Significant peaks are marked with vertical lines: blue (radial pulsations and additional signals, f_FU for the fundamental mode, f_1O for the first overtone, and f_X for others), red (harmonics, subharmonics, and combination signals; f_i, i = 0, 1, 2, …), and green (aliases; a_i, i = 0, 1, 2, …). Blue horizontal lines indicate FAL probabilities of p = 0.1, 0.01, and 0.001 (bottom to top).