Spectrum around 6 μm and the best-fit H₂O model for f_bg = 0.35. The top panel shows the absolute flux spectrum and continuum model. The middle panel shows the continuum-normalised spectrum. Strong H₂O lines are labelled by their upper- and lower-level quantum numbers as J_u,K_a,u,K_c,u−J_l,K_a,l,K_c,l. Several strong emission lines and absorption lines of C₂H are labelled as well. The pink shaded area indicates the spectral region considered in the fit. The bottom panel shows the residuals on the continuum-normalised spectrum; the grey shaded area indicates their 68% interval.