Comparison between the SED of IRC +10 216 as modeled and as observed by ISO at φ = 0.24. Wavelengths of some vibrational transitions of HNC are indicated by vertical lines. The vibrational transition indicated at  ~11 μm correspond to the 000  →  020 vibrational band and the transition at  ~21 μm to the 000  →  010 and 010  →  020 bands. The dotted vertical line around 45 μm indicates the ISO LWS/SWS division. The inset panel shows the computed SED at different phases.