Full normalised spectrum acquired on September 20, 2019, during the hard X-ray spectral state. The position of some of the most relevant emission lines is highlighted with dashed blue (He I 5876 Å and 6678 Å), red (H_α and H_β), and green (He II) lines. The Na interstellar doublet is marked in yellow. The two insets show zoomed-in views of the normalised spectrum in velocity scale for the H_β and H_α lines; dotted-dashed blue lines provide the wind velocities measured in the system in previous studies.