Line profiles for different optical depth of the CSM. The black with τ_e = 7.9 corresponds to the best fit model at +48 days. The velocity of the emitting shell behind the shock is in all cases V_em in = 5390 km s⁻¹ and V_em out = 6160 km s⁻¹. One notes the gradual transition from highly skewed profiles to symmetric as the optical depth increases. In all cases, an electron temperature of 15 000 K is assumed.