Cross-correlation function decomposition of ϵ Eri with a Hermite basis. Left: contribution of consecutive basis components to the differential CCF reconstruction. We displayed six illustrative epochs randomly selected to visualise the temporal variability of the line-shape distortions. The observed differential CCFs are shown in grey, while the reconstructed components are colour-coded according to the observation time. Middle: time series of the corresponding coefficients. Right: GLS periodograms of the coefficients. The 0.1%, 1%, and 10% FAP levels are indicated in orange, and the stellar rotation period and its first harmonic are marked in purple.