The ultraviolet range of spectra used in this study for TW Hya (red curve, France et al. 2014; Cleeves et al. 2015) and HD 100546 (blue curve, Bruderer et al. 2012), compared with blackbody photospheres for pre main sequence model stars with an age of 10 Myr (black curves, Tognelli et al. 2011). The two curves labelled 4000 K+UV show a 4000 K stellar photosphere with a 10 000 K blackbody added for the accretion rates Ṁ= 10^-9 and 10^-8 M_⊙ yr^-1. See also Table 3.