# A population study of gaseous exoplanets

## TL;DR

This study analyzes 30 gaseous exoplanets using HST data, introducing the Atmospheric Detectability Index to assess atmospheric presence, finding water vapour in all detectable atmospheres and TiO/VO in select cases, with implications for future surveys.

## Contribution

The paper presents a large, self-consistent analysis of exoplanet atmospheres, introducing the Atmospheric Detectability Index to quantify atmospheric detection significance.

## Key findings

- Statistically significant atmospheres detected around 16 of 30 planets.
- Water vapour detected in all atmospheres with detectable signals.
- TiO/VO signatures identified in WASP-76 b and likely in WASP-121 b.

## Abstract

We present here the analysis of 30 gaseous extrasolar planets, with temperatures between 600 and 2400 K and radii between 0.35 and 1.9 $R_\mathrm{Jup}$. The quality of the HST/WFC3 spatially scanned data combined with our specialized analysis tools allow us to study the largest and most self-consistent sample of exoplanetary transmission spectra to date and examine the collective behavior of warm and hot gaseous planets rather than isolated case-studies. We define a new metric, the Atmospheric Detectability Index (ADI) to evaluate the statistical significance of an atmospheric detection and find statistically significant atmospheres around 16 planets out of the 30 analysed. For most of the Jupiters in our sample, we find the detectability of their atmospheres to be dependent on the planetary radius but not on the planetary mass. This indicates that planetary gravity plays a secondary role in the state of gaseous planetary atmospheres. We detect the presence of water vapour in all of the statistically detectable atmospheres, and we cannot rule out its presence in the atmospheres of the others. In addition, TiO and/or VO signatures are detected with 4$\sigma$ confidence in WASP-76 b, and they are most likely present in WASP-121 b. We find no correlation between expected signal-to-noise and atmospheric detectability for most targets. This has important implications for future large-scale surveys.