Temporal distribution of residuals in λ-space for three representative line profiles in HD 2905. (Left) Si III λ4567 as an example of a purely photospheric line. (Right) H_α as the most extreme case of optical line affected by stellar wind. (Middle) H_β as an intermediate case. We also include for reference purposes three sinusoidal curves with associated frequencies 0.055 d⁻¹ (pink), 0.019d⁻¹ (blue), and 0.369 d⁻¹ (purple), respectively (see Sect. 4.2.3 for discussion). Panels to the left show the temporal variation of the centroid of each line-profile (⟨v⟩). Bottom panels include several individual profiles corresponding to the dates indicated as horizontal lines in the left panels, as well as the mean profile obtained from the complete FIES+HERMES+SONG spectroscopic dataset.