Transmission spectrum of the He I triplet during transit. Measured absorption (+), and their respective estimated errors, are shown in black. The data are the same as in Fig. 3 but with a three-point running mean applied. The cyan curve shows the absorption profile when only the Doppler and turbulence broadenings are included. The red curve is the best-fit model obtained for an effective temperature of 6000 K, a mass-loss rate (Ṁ) of 3 × 10¹⁰ g s⁻¹ and a H/He mole-fraction ratio of 90/10. This calculation included, in addition to the Doppler and turbulence broadenings, the broadening induced by the radial velocities of the model and an additional blue net wind of –3.2 km s⁻¹. The positions of the three He I lines are marked by vertical dotted lines.