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Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

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Cabot, SHC 
Madhusudhan, N 
Welbanks, L 
Piette, A 
Gandhi, S 


The class of ultra-hot Jupiters comprises giant exoplanets undergoing intense irradiation from their host stars. They have proved to be a particularly interesting population for their orbital and atmospheric properties. One such planet, WASP-121~b, is in a highly misaligned orbit close to its Roche limit, and its atmosphere exhibits a thermal inversion. These properties make WASP-121~b an interesting target for additional atmospheric characterization. In this paper, we present analysis of archival high-resolution optical spectra obtained during transits of WASP-121~b. Artifacts from the Rossiter-McLaughlin effect and Center-to-Limb Variation are deemed negligible. However, we discuss scenarios where these effects warrant more careful treatment by modeling the WASP-121 system and varying its properties. We report a new detection of atmospheric absorption from Hα in the planet with a transit depth of 1.87±0.11%. We further confirm a previous detection of the Na I doublet, and report a new detection of Fe I via cross-correlation with a model template. We attribute the Hα absorption to an extended Hydrogen atmosphere, potentially undergoing escape, and the Fe I to equilibrium chemistry at the planetary photosphere. These detections help to constrain the composition and chemical processes in the atmosphere of WASP-121~b.



planets and satellites: atmospheres

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Monthly Notices of the Royal Astronomical Society

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Oxford University Press (OUP)


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Science and Technology Facilities Council (ST/N000927/1)