Assessment of the Metallicity of the Atmospheres of Ultra-Hot Jupiter WASP‑121b and WASP‑76b based on Observations in the Lines of He(I) and Fe(II) and Numerical Simulation Using Non-LTE Kinetics

The paper presents the results of modeling the atmospheres of planets that are part of morphologically similar planetary systems—the ultra-hot Jupiters WASP-121b and WASP-76b. For the first time, the absorption in the Fe(II) 501.8-nm line was calculated using a complete kinetic modeling of the population of excited iron levels. Together with the absorption calculations in the 1083-nm metastable helium line, comparison with observations allowed us to estimate two important parameters: the flux of ionizing radiation from the star and the metallicity of the planets’ atmospheres. The modeling results showed that at supersolar abundances of heavy elements, strong compression of the atmosphere occurs, while subsolar abundances are consistent with the observed absorptions.