Identified lines of C₂H₃CHO: the synthetic spectrum, in red, is plotted along with the offset position spectrum towards IRAS 16293B. 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 reference spectrum in blue takes the previous species reported in PILS into account (Jørgensen et al. 2016, 2018; Lykke et al. 2017; Coutens et al. 2016; Ligterink et al. 2017; Persson et al. 2018; Calcutt et al. 2018a; Drozdovskaya et al. 2018; Manigand et al. 2019).