CH₃CN(J = 6 − 5), K = 0–5 spectrum observed in IRAS 4A with PdBI, corresponding to the continuum peak coordinates of A1 (green) and A2 (black). The spectrum of A1 was smoothed to a channel width of 1 km s^-1. The Gaussian fits to the lines detected in A2 are depicted in blue (see Table 2). The positions of the different K transitions, from K = 0 (left) to K = 5 (right), are indicated in red.