Rotation diagrams for ¹³CH₃OH (upper panel) and CH₂DOH (lower panel). An emitting region size of is assumed (see text). The parameters N_u, g_u, and E_up are the column density, the degeneracy, and the energy of the upper level, respectively. The derived value of the rotational temperature is reported for ¹³CH₃OH. For CH₂DOH the T_rot derived from the ¹³C-isotopologues is assumed to derive the column density. The two CH₂DOH transitions with excitation energies higher than 400 K as well as the Cycle 4 point are excluded from the fit, although they are in good agreement with it.