ARES II: Characterising the Hot Jupiters WASP-127 b, WASP-79 b and WASP-62 b with HST

TL;DR

This study characterizes the atmospheres of three hot Jupiters using HST data, revealing water and iron hydride features, with WASP-127b being notably low-density and a prime target for future observations.

Contribution

First detailed atmospheric characterization of WASP-127b, WASP-79b, and WASP-62b using HST G141 spectroscopic data and advanced retrieval techniques.

Findings

WASP-127b shows strong water absorption and signs of iron hydride.

Water vapour detected in WASP-79b and WASP-62b atmospheres.

All three planets are promising targets for JWST and Ariel.

Abstract

This paper presents the atmospheric characterisation of three large, gaseous planets: WASP-127b, WASP-79b and WASP-62b. We analysed spectroscopic data obtained with the G141 grism (1.088 - 1.68 $\mu$m) of the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST) using the Iraclis pipeline and the TauREx3 retrieval code, both of which are publicly available. For WASP-127 b, which is the least dense planet discovered so far and is located in the short-period Neptune desert, our retrieval results found strong water absorption corresponding to an abundance of log(H$_2$O) = -2.71$^{+0.78}_{-1.05}$, and absorption compatible with an iron hydride abundance of log(FeH)=$-5.25^{+0.88}_{-1.10}$, with an extended cloudy atmosphere. We also detected water vapour in the atmospheres of WASP-79 b and WASP-62 b, with best-fit models indicating the presence of iron hydride, too. We used the Atmospheric Detectability Index (ADI) as well as Bayesian log evidence to quantify the strength of the detection and compared our results to the hot Jupiter population study by Tsiaras et al. 2018. While all the planets studied here are suitable targets for characterisation with upcoming facilities such as the James Webb Space Telescope (JWST) and Ariel, WASP-127 b is of particular interest due to its low density, and a thorough atmospheric study would develop our understanding of planet formation and migration.