Notes. The reduced chi-square, , is obtained from Eq. (C.1). The frequency continuum slope, α_ν, is computed from the wavelength continuum slope, α_λ = −α_ν − 2, where the continuum is modelled through a power law of the form C_λ ∝ λ^α_λ. In Fig. 33, the continuum is plotted as the lowest line joining the two most widely separated points in the range 121 − 600 nm without crossing the spectrum in this range. The emission line location, λ_obs, and maximal line flux density, F, are retrieved from the fit of a quadratic polynomial in the vicinity of the laboratory wavelength, λ_lab, after a local continuum has been subtracted that was computed in the same way as for α_λ. The full-width at half maximum (FWHM) is retrieved from these continuum-subtracted emission lines using a linear interpolation of the spectral flux densities. All uncertainties are calculated, to first order, using the formal uncertainties on the composite spectra obtained from Eq. (C.4).