ARES III: Unveiling the Two Faces of KELT-7 b with HST WFC3

TL;DR

This study uses HST WFC3 spectroscopy to analyze KELT-7b, revealing a cloud-free atmosphere with water and H- in transmission, while emission spectra suggest complex atmospheric processes without clear molecular features.

Contribution

First combined transmission and emission spectroscopy analysis of KELT-7b with HST WFC3, revealing atmospheric composition and structure complexities.

Findings

Transmission spectrum indicates water and H- presence.

Emission spectrum suggests complex temperature-pressure profile.

Atmospheric features require further observations for confirmation.

Abstract

We present the analysis of the hot-Jupiter KELT-7b using transmission and emission spectroscopy from the Hubble Space Telescope (HST), both taken with the Wide Field Camera 3 (WFC3). Our study uncovers a rich transmission spectrum which is consistent with a cloud-free atmosphere and suggests the presence of H2O and H-. In contrast, the extracted emission spectrum does not contain strong absorption features and, although it is not consistent with a simple blackbody, it can be explained by a varying temperature-pressure profile, collision induced absorption (CIA) and H-. KELT-7 b had also been studied with other space-based instruments and we explore the effects of introducing these additional datasets. Further observations with Hubble, or the next generation of space-based telescopes, are needed to allow for the optical opacity source in transmission to be confirmed and for molecular features to be disentangled in emission.