Detailed comparison of some of the emission lines presented in Fig. 2. The characteristic wind velocities (from MD19) are marked as dashed (±1200 km s⁻¹) and dash-dotted (±1800 km s⁻¹) vertical lines. The colour code reflects the different X-ray states as in Fig. 2. The Na interstellar doublet in the red wing of He I–5876 is shaded. Top left panel: Paδ (epoch 1) and Paβ (epochs 3 and 4) during the rising phase of the outburst. Blue-shifted absorption troughs with a blue-edge velocity of ∼1200 km s⁻¹ are visible. These are compared with the He I–5876 P Cyg profile from epoch 1. Top right panel: two soft-state epochs (4 and 5) of Paβ against the He I–5876 P Cyg profile from epoch 1. Bottom left panel: Paβ and Brγ from epoch 4 showing clear differences in the blue part of the line up to ∼200 km s⁻¹. Bottom right panel: He I–5876 (epoch 8) showing a P Cyg profile with a terminal velocity of ∼1800 km s⁻¹. Paβ (also epoch 8) displays a double-peaked profile whose blue wing reaches higher velocities (∼1800 km s⁻¹) than the red wing. The flux scale in this panel is different from that of the previous panels.