Refractory and Volatile Species in the UV-to-IR Transmission Spectrum of Ultra-hot Jupiter WASP-178b with HST and JWST

Résumé fourni par la source

Abstract The atmospheres of ultra-hot Jupiters are unique compared to other planets because of the presence of both refractory and volatile gaseous species, enabling a new lens to constrain a planet’s composition, chemistry, and formation. WASP-178b is one such ultra-hot Jupiter that was recently found to exhibit enormous near-UV absorption between 0.2 and 0.4 μ m from some combination of Fe+, Mg, and SiO. Here, we present new IR observations of WASP-178b with the Hubble Space Telescope (HST) WFC3 and JWST NIRSpec G395H, providing novel measurements of the volatile species H 2 O and CO in WASP-178b’s atmosphere. Atmospheric retrievals find a range of compositional interpretations depending on which data set is retrieved, the type of chemistry assumed, and the temperature structure parameterization used due to the combined effects of thermal dissociation, the lack of volatile spectral features besides H 2 O and CO, and the relative weakness of H 2 O and CO themselves. Taken together with a new state-of-the-art characterization of the host star, our retrieval analyses suggests a solar to supersolar [O/H] and [Si/H], but subsolar [C/H], perhaps suggesting rock-laden atmospheric enrichment near the H 2 O ice line. To obtain meaningful abundance constraints for this planet, it was essential to combine the JWST IR data with short-wavelength HST observations, highlighting the ongoing synergy between the two facilities.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.