Evolution of the main NIR emission lines across the outburst. The optical transitions Hα and He I–5876 lines are also included for comparison. Every line is plotted normalised in a separate panel, with the exception of He I–10 830 and Paγ, which share axes due to their proximity. He II at 10 124 Å can also be seen in the Paδ panels, especially during the soft-state epochs. The characteristic wind velocities determined in MD19 are plotted as dashed (1200 km s⁻¹) and dash-dotted (1800 km s⁻¹) lines.