Undetected lines of 3-hydroxypropenal that are predicted above 3σ with the new spectroscopic data and the parameters previously constrained by Coutens et al. (2022) for an excitation temperature T_ex = 300 K. The PILS observations are in black. The model in red has been obtained with the best-fit parameters derived by Coutens et al. (2022) for T_ex = 300 K, i.e. with a column density N=l.8×l0¹⁵ cm². For comparison, the model obtained for T_ex = 125 K (N = 1.0 × 10¹⁵ cm²) is added in magenta. The cyan dotted line represents the 3 rms level per 0.33 km s⁻¹ (1/3 of the line width).