Position, strength, and shape of He I lines. The vertical lines denote the central wavelength of the lines and the horizontal line the position of the continuum. The color distinguishes the singlet (red) and triplets (blue) states. All spectral lines are plotted on the same scale, which suppresses the strength of the emission wings of He I 5 876 and 6 678 Å lines. We note that the continuum normalization was carried out very carefully.