Fig. 4. The spectral difference between 12CO2 and 13CO2. Top : pure 12CO2 T=800 K, N=10 cm-2; Bottom : pure 13CO2 T=800 K, N=10 cm-2; middle : the observed continuum subtracted spectrum of EP Aqr. All spectra are normalized to the maximum intensity and are hence only illustrative for the different band positions, not the band intensities. The insets show blow-ups of the 15.4 and 16.2 regions.