Identified lines of C₃H₆: the synthetic spectrum, in red, is plotted along with the offset position spectrum towards IRAS 16293B. The dashed lines correspond to optically thick lines. The straight dashed black line represents the detection limit at the intensity of 3σ. The upper-level energy of the transition is noted in the upper left corner of each panel. The torsional state “E” or “A” of each transition is noted in green on the spectra. The reference spectrum in blue takes the previous species reported in PILS into account (see Fig. 2 and references therein).