Position–velocity plots along a direction with PA = +37° passing through the continuum peak. The crosses in the bottom left corners denote the spatial and spectral resolutions. Contour levels (in units of brightness temperature in the synthesized beam) range: from 4 to 82 in steps of 13 K (1σ RMS ≃ 1.2 K) for the K = 2 line; from 4 to 74 in steps of 14 K (1σ RMS ≃ 1.2 K) for the K = 3; from 3 to 66 in steps of 9 K (1σ RMS ≃ 0.67 K) for the K = 4; from 2 to 26 in steps of 3 K (1σ RMS ≃ 0.42 K) for the K = 2 line of CH₃¹³CN; from 1 to 10 in steps of 3 K (1σ RMS ≃ 0.61 K) for the K = 8; and from 1 to 26 in steps of 5 K (1σ RMS ≃ 0.24 K) for the K,l = 1,1 line. The dashed horizontal and vertical lines correspond to the systemic velocity and position of the 1.4 mm continuum peak. The “butterfly-shaped” patterns in the K = 3 panel outline the regions inside which emission is expected if the gas lies in a disk with radius of 0.̋75 (~1200 AU), rotating about a 7 M_⊙ star (solid pattern) and a 10 M_⊙ star (dashed).