Amplitude and phase variations obtained when assuming the multiplet around F1 is solely due to an individual frequency at F1. Top panel: amplitude variations obtained from fitting F1 to subsets of the multiplet light curve (black points), the binned values (red points), and the cubic spline interpolation used as model (red line). Middle panel: same as the top panel but for phase variations. Bottom panel: amplitude spectra of the multiplet light curve (black line) and of the resulting model flux (dashed red line).