Same as Fig. A.4, but for models with fixed values of T = 2400 K, N_CO = 4 × 10²¹ cm⁻², and v_rot sini = 130 km s⁻¹. Coloured solid lines represent models with different values of the intrinsic line width: Δv = 10 km s⁻¹ (solid green line), Δv = 15 km s⁻¹ (solid red line), and Δv = 20 km s⁻¹ (solid blue line). The data are smoothed at a resolution of R = 1000. When the data are smoothed the first bandhead becomes smaller because the line peak has only a few points, which causes the second and third bandhead to exceed than the unsmoothed spectra when we normalise.