Transitions listed in Table C.1 and used to fit ¹³CH₃NCO. The turquoise curve represents the best LTE fit obtained with MADCUBA (Table 1). The red curve shows the simulated spectrum taking into account all the species identified so far in the region. Note that at 108.406 GHz the baselinederived from STATCONT is slightly high, and the simulated spectra do not match exactly the observed one.