Retrieved transmission spectra, abundance constraints, and P-T profile with free-chemistry retrievals. The top panel consists of median transmission spectra and P-T profiles of HD 209458 b for the three retrievals, JWST (NIRCam), HST WFC3 + JWST NIRCam, and HST STIS + HST WFC3 + JWST NIRCam. All the spectra shown here are generated with 5000 random equal-weighted samples from PyMultiNest and binned at a resolution of R ∼ 200. The shaded region indicates the 1σ uncertainty in the median fit. JWST observations are represented in green, while combined STIS and WFC3 observations are shown in brown. A retrieved median offset of 204 ppm is applied to the HST observations, whereas the offset for WFC3 in the case of the WFC3+NIRCam combination is not shown here. For all the retrievals, the corresponding P-T profiles are shown beside the median spectra. The middle panel shows the posteriors of the logarithm of mixing ratios of the ten molecules for three retrievals. The bottom panel shows the posteriors of the clouds and hazes parameters.