Top: S/N of the H₂O cross-correlation signal obtained for different wavelength intervals (indicated by horizontal bars) for HD 209458 b (black and open circles) and HD 189733 b (magenta triangles) with CARMENES. The 1σ uncertainties are indicated by the vertical bars. The results in the 0.96–1.71 μm spectral region were obtained with one transit for HD 209458 b and HD 189733 b in Sánchez-López et al. (2019). Open symbols show spectral regions for which the measurements of HD 209458 b are uncertain due to a problematic telluric removal. The larger signal towards shorter wavelengths in HD 209458 b compared to HD 189733 b is indicative of the higher atmospheric transparency of the former planet. Bottom: model H₂O transmission spectra for HD 209458 b assuming a clear atmosphere (black) and for HD 189733 b including a stronger haze extinction at an arbitrary level (magenta). The spectrum of HD 209458 b is offset by 10⁻² for illustration purposes.