Illustration of the total flux (black) and that due to He I bound-bound transitions (red) in the spectral regions centered on 3888.6, 4471.5, 5875.7, 6678.1, and 7065.2 Å. In each panel, a normalization is applied so that the total flux peaks at one – the same normalization is then used for the He I spectrum. A vertical offset between the two curves is typically caused by Fe II emission. To erase a small level of high-frequency noise in the models, all spectra have been convolved with a Gaussian kernel (with a FWHM of 4.7 Å– standard deviation of 2.0 Å).