Illustration of ejecta and radiative properties of model r1w6b at 5 d after explosion, as computed by HERACLES and CMFGEN. From top to bottom, we show the variation with radius of the mass density (dots correspond to the CMFGEN radial grid) ; the electron-scattering optical depth τ_es (solid black curve) together with the regions of formation of Hα, He II 4685.7 Å, and N III 4640.6 Å (denoted $\overline{\zeta }$; ζ is defined such that ∫_a^bζdr gives the fractional line flux originating between radii a and b, and for better visibility we show its scaled value $\overline{\zeta }$; for details see Hillier 1987), and the scaled cumulative fractional bolometric luminosity ${\displaystyle \sum \delta }\overline{L}$ (dashed black curve); the temperature together with the H, He, and N ionization γ (a value of γ of one means that the corresponding species is once ionized) ; and the original, nonmonotonic velocity from the HERACLES simulation (dashed line) together with the fudged, homologous velocity adopted for the CMFGEN calculation (solid line). See the discussion in Sect. 2.