χ² maps for the ¹²CO₂,¹³CO₂, C₂H₂, and H₂O slab model fits in the 13.5-17.5 µm wavelength range. The color-scale indicates ${\chi }_{\min }^2/{\chi }^2$, the three black contours correspond to the 1σ, 2σ, and 3σ levels, and the white contours show the emitting radii in au. The best-fit model is indicated with a blue cross, and corresponds to ${\chi }_{\min }^2/{\chi }^2=1$. On the bottom-right panel, the best H₂O fit using the isolated lines from Tables 6 and 7 from Banzatti et al. (2024) is depicted with a white star.