Ca I 4226 Å and Mg  II 4481 Å lines observed with FEROS during the night of 2016-03-28/29. The spectra have been rebinned to a pixel spectral resolution of 6.39 km s⁻¹. The date and UT of each spectrum are indicated. Black dashed line: median of the four-day period shown for comparison. We note the different behaviour of the extra absorption features of each line when compared to their median spectra. The vertical dashed line corresponds to a radial velocity of 3 km s⁻¹ (see text in Sect. 4.2 and Fig. 5).