Spectral Retrieval with JWST Photometric data: a Case Study for HIP 65426 b

TL;DR

This study demonstrates how JWST photometric data, combined with archival spectra, can be used to retrieve atmospheric properties of exoplanets like HIP 65426 b, providing insights into their composition and cloud features.

Contribution

It shows the potential and limitations of using only photometric data for atmospheric retrievals of exoplanets.

Findings

Consistent with solar metallicity and C/O ratios around 0.40-0.55.

Rules out high metallicity and C/O=1.0 atmospheres.

Detects silicate clouds but no dust extinction features.

Abstract

Half of the JWST high-contrast imaging objects will only have photometric data {{as of Cycle 2}}. However, to better understand their atmospheric chemistry which informs formation origin, spectroscopic data are preferred. Using HIP 65426 b, we investigate to what extent planet properties and atmospheric chemical abundance can be retrieved with only JWST photometric data points (2.5-15.5 $\mu$m) in conjunction with ground-based archival low-resolution spectral data (1.0-2.3 $\mu$m). We find that the data is consistent with an atmosphere with solar metallicity and C/O ratios at 0.40 and 0.55. We rule out 10x solar metallicity and an atmosphere with C/O = 1.0. We also find strong evidence of silicate clouds but no sign of an enshrouding featureless {{dust}} extinction. This work offers guidance and cautionary tales on analyzing data in the absence of medium-to-high resolution spectral data.