Rotational diagrams for OCS derived using the emission lines observed towards SVS13-A (see Table 1 and Fig. 9). The parameters N_u, g_u, and E_up are, respectively, the column density, the degeneracy, and the energy (with respect to the ground state of each symmetry) of the upper level. A source size of 0.′′ 3 has been assumed, following the SO, SO₂, and H₂CS LVG analysis. The derived values of the rotational temperature are reported in the panels.