Data from "BOWIE-ALIGN: weak spectral features in KELT-7b’s JWST NIRSpec/G395H transmission spectrum imply a high cloud deck or a low-metallicity atmosphere"

Hot Jupiters and their atmospheres are prime targets for transmission spectroscopy due to their extended atmospheres and the corresponding large signal-to-noise, providing the best possible constraints for the atmospheric carbon-to-oxygen (C/O) ratio and metallicity of exoplanets.
Within BOWIE-ALIGN, we aim to compare JWST spectra of a sample of orbitally aligned and misaligned hot Jupiters orbiting F-type stars to probe the link between hot Jupiter atmospheres and planet formation history.
Here, we present a near-infrared transmission spectrum of the aligned planet KELT-7b using one transit observed with JWST NIRSpec/G395H. We find weak features, only tentative evidence for H2O and CO2 in the atmosphere of KELT-7b. This poses a challenge to constrain the atmospheric properties of KELT-7b and two possible scenarios emerge from equilibrium chemistry and free chemistry retrievals: a high-altitude cloud deck muting all features or an extremely low metallicity atmosphere. The retrieved C/O ratios from our data reductions range from 0.43 - 0.74, while the atmospheric metallicity is suggested to be stellar to super-stellar (1-16 x solar). We are unable to place sufficient constraints on the C/O ratio or metallicity to be able to place direct constraints on KELT-7b's formation history.