Assessing the quality of CARMENES observations for the potential detection of H₂O in the atmosphere of HD 332231 b. Top panel: example of a transmission model calculated with petitRADTRANS (T_eq = 876 K and [Fe/H] = 0), normalised to a baseline estimated from the continuum species only and convolved with the instrumental profile. Bottom panel: detection significances for the injected models, smoothed with a Gaussian filter of σ = 1. The expected location of HD 332231 b’s atmosphere for its estimated equilibrium temperature and assumed solar metallicity has been indicated as the red data point.