Range of the neutral hydrogen concentration profiles (in grey shade areas) resulting from the fit of the measured absorption (filled circles in Fig. 4) for HD 189733 b (upper panels), GJ 3470 b (lower panels), and several H/He ratios, as labelled. The solid thicker curves are the mean profiles. The H⁰ density derived from Lyα measurements for HD 189733 b and GJ 3470 b by Salz et al. (2016) and our estimated uncertainties (× 10 and /10 for HD 189733 b, as well as ×10 and / for GJ 3470 b) are also shown (diamonds and hatched areas in magenta). The red profile is the H⁰ density derived by Odert et al. (2020) from their SF11 model for HD 189733 b.