Spectrum of CH₃CN and CH₃¹³CN toward the peak of the continuum emission. The labels of the line frequencies, blue (CH₃CN), orange (CH₃¹³CN), grey and pink bars, are shifted assuming a systemic velocity of 8.1 km s⁻¹. We only marked lines with an Einstein coefficient > 10⁻⁶ s⁻¹ and E_up < 500 K; the Einstein coefficients are 6 × 10⁻⁶ s⁻¹ (E_up = 382 K) for the CH₃OCHO line and 1 × 10⁻⁴ s⁻¹ (E_up = 50 K) for the ³³SO₂ line in pink while both are very weak or undetectable based on the XCLASS model from wideband spectra including more transitions. The horizontal dashed line indicates the continuum level of 5.8 K determined from line free channels. The sensitivity per channel is 380 mK.