Representative model and data of the bright state of the spectrum. Blue corresponds to the model and red to the observations. The intensity is normalised to the second bandhead and the wavelength is in microns. Five bandheads are shown (υ = 2- 0, 3-1, 4-2, 5-3, and 6-4). The parameters of the model are listed in Table 2. This particular case is for T = 3000 K, N_CO = 8 × 10²⁰ cm⁻², and v_k sin i = 113 km s⁻¹.