Major chemical species contributing to gas absorption features. Top panel: solid line is the median model shown in the lower panel of Fig. 5. The dashed line is the same atmospheric model but assuming zero abundance of H₂O, CH₄, and NH₃. The transmission spectra of OB12 and OB13 have been corrected for stellar contamination. Middle panel: contributions of gas absorption to the transmission spectra. Bottom panel: posterior distributions of the major species’ volume mixing ratios.