Extended Data Table 1.

TESS and JWST NIRISS/SOSS fit results

The median and 1σ uncertainties of the astrophysical parameters from the TESS (left column) and JWST NIRISS/SOSS (right column) analyses of WASP-18. The transit observations in the TESS phase curve are fitted considering the u₁ and u₂ quadratic limb-darkening coefficients. In our TESS phase-curve parametrization, the secondary-eclipse depth and nightside flux are derived parameters calculated from the average relative planetary flux ${\overline{f}}_{\mathrm{p}}$ and the phase-curve semiamplitude F_atm of the planet. Likewise, the orbital inclination i is derived from the scaled semi-major axis a/R_* and the impact parameter b. The parameters fixed to the values from the TESS analysis for the NIRISS/SOSS light-curve fitting are shown without uncertainties in the table. The retrieved parameters are the time of secondary eclipse T_sec, the impact parameter b and the semimajor axis a/R_*, the last two being fitted considering normal priors from the TESS constraints. The NIRISS/SOSS eclipse depth is derived from the samples of the astrophysical model (equation (4)).