Left: Circumstellar Ca  II H (up) and K (bottom) features of the HERMES spectra taken in December 2015. The photospheric line has been removed as estimated from Kurucz synthetic models (this is the procedure followed for all Ca II H and K plots, see Sect. 4.2). The spectra have been rebinned to 3 pixels (size 3.56 km s⁻¹). Right (bottom): Ca  II 8542 Å. The spectra have been rebinned to a resolution of 3.29 km s⁻¹ per pixel. Right (up) Fe  II 5169 Å line; the pixel resolution in this case is 8.16 km s⁻¹. The photospheric contribution is not removed in the right panels (this is the procedure for all plots of these lines). Dates are colour-coded. The vertical dashed line corresponds to a radial velocity of 3 km s⁻¹ (this line is plotted in all plots). For comparison, and to visualise the CS contribution, the right panels also show in black the Fe II 5169 Å and Ca II 8542 lines of the ϕ Leo Kurucz model and the observed spectrum of the star α Aql.