Retrieved spectra with the WASP-39 b Tiberius data. The solid curves show the best-fit retrieved spectra obtained from the pRT baseline retrieval (including H₂O) and the ones with added SO₂ and CH₄, as described in Section 4.1.2. We see that SO₂ and CH₄ both improve the fit in a similar wavelength range (≈7.5−8 μm), hence their partial degeneracy described in Appendix D.2. We note that the last data point at 11.375 μm is below the figure, with a transit depth of ﹩1.7{5}_{-0.117}^{+0.117} \% ﹩.