Tracing the formation and migration history: molecular signatures in the atmosphere of misaligned hot Jupiter WASP-94Ab using JWST NIRSpec/G395H

Abstract

The discovery of hot Jupiters that orbit very close to their host stars has long challenged traditional models of planetary formation and migration. Characterising their atmospheric composition - mainly in the form of the carbon-to-oxygen (C/O) ratio and metallicity - can provide insights into their formation locations and evolution pathways. With JWST we can characterise the atmospheres of these types of planets more precisely than previously possible, primarily because it allows us to determine both their atmospheric oxygen and carbon composition. Here, we present a JWST NIRSpec/G395H transmission spectrum from 2.8-5.1$\mu m$ of WASP-94Ab, an inflated hot Jupiter with a retrograde misaligned orbit around its F-type host star. We find a relatively cloud-free atmosphere, with absorption features of H${}_2$O and CO${}_2$ at detection significances of $\sim 4\sigma$ and $\sim 11\sigma$, respectively. In addition, we detect tentative evidence of CO absorption at $\sim 3\sigma$, as well as hints of sulphur with the detection of H${}_2$S at a $\sim 2.5\sigma$ confidence level. Our favoured equilibrium chemistry model determines a C/O ratio of $0.49_{-0.13}^{+0.08}$ for WASP-94Ab's atmosphere, which is substellar compared to the star's C/O ratio of $0.68\pm 0.10$. The retrieved atmospheric metallicity is similar to the star's metallicity as both are $\sim 2\times$ solar. We find that this sub-stellar C/O ratio and stellar metallicity can be best explained by pebble accretion or planetesimal accretion in combination with large-distance migration of the planet.

19 pages, 15 figures, accepted for publication in MNRAS

References in corpus (39)

• Bayes in the sky: Bayesian inference and model selection in cosmology
• petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval
• The effect of red noise on planetary transit detection
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• Towards Chemical Constraints on Hot Jupiter Migration
• ExoMol molecular line lists XXXV: a rotation-vibration line list for hot ammonia
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• Chemical enrichment of giant planets and discs due to pebble drift
• ExoMol molecular line lists - XVI: The rotation-vibration spectrum of hot H${}_2$S
• Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H${}_2$O, Na, and K
• ExoMol line lists -- XXXIX. Ro-vibrational molecular line list for CO${}_2$
• Oxygen Abundances in Nearby Stars. Clues to the formation and evolution of the Galactic disk
• The Kozai-Lidov Mechanism in Hydrodynamical Disks
• The Stagger-grid: A grid of 3D stellar atmosphere models - IV. Limb darkening coefficients
• Planet-forming material in a protoplanetary disc: the interplay between chemical evolution and pebble drift
• Carbon and oxygen abundances in stellar populations
• ExoMol molecular line lists -- XXXVII: spectra of acetylene
• Jupiter's composition suggests its core assembled exterior to the N2 snowline
• Likely Transiting Exocomets Detected by Kepler
• On the tidal origin of hot Jupiter stellar obliquity trends
• Transiting exocomets detected in broadband light by TESS in the $\beta$ Pictoris system
• Marvel analysis of the measured high-resolution rovibrational spectra of H2S
• WASP-94 A and B planets: hot-Jupiter cousins in a twin-star system
• HyDRA-H: Simultaneous Hybrid Retrieval of Exoplanetary Emission Spectra
• A Benchmark JWST Near-Infrared Spectrum for the Exoplanet WASP-39b
• Awesome SOSS: Atmospheric Characterisation of WASP-96 b using the JWST Early Release Observations
• Constraining mornings & evenings on distant worlds: a new semi-analytical approach and prospects with transmission spectroscopy
• Quartz Clouds in the Dayside Atmosphere of the Quintessential Hot Jupiter HD 189733 b
• ExoTiC-LD: thirty seconds to stellar limb-darkening coefficients
• The composition of hot Jupiter atmospheres assembled within chemically evolved protoplanetary discs
• Evidence that the Hot Jupiter WASP-77 A b Formed Beyond Its Parent Protoplanetary Disk's H2O Ice Line
• LRG-BEASTS: sodium absorption and Rayleigh scattering in the atmosphere of WASP-94A b using NTT/EFOSC2
• Spirals, shadows & precession in HD 100453 -- I. The orbit of the binary
• Spirals, shadows & precession in HD 100453 -- II. The hidden companion
• Detection of carbon monoxide's 4.6 micron fundamental band structure in WASP-39b's atmosphere with JWST NIRSpec G395H
• JWST COMPASS: NIRSpec/G395H Transmission Observations of the Super-Earth TOI-776b
• Catwoman: A transit modelling Python package for asymmetric light curves
• Hint of an exocomet transit in the CHEOPS lightcurve of HD 172555
• A First Look at the JWST MIRI/LRS Phase Curve of WASP-43b