Climate of an Ultra hot Jupiter: Spectroscopic phase curve of WASP-18b with HST/WFC3

Abstract

We present the analysis of a full-orbit, spectroscopic phase curve of the ultra hot Jupiter WASP-18b, obtained with the Wide Field Camera 3 aboard the Hubble Space Telescope. We measure the planet's normalized day-night contrast as >0.96 in luminosity: the disk-integrated dayside emission from the planet is at 964+-25 ppm, corresponding to 2894+-30 K, and we place an upper limit on the nightside emission of <32ppm or 1430K at the 3-sigma level. We also find that the peak of the phase curve exhibits a small, but significant offset in brightness of 4.5+-0.5 degrees eastward. We compare the extracted phase curve and phase resolved spectra to 3D Global Circulation Models and find that broadly the data can be well reproduced by some of these models. We find from this comparison several constraints on the atmospheric properties of the planet. Firstly we find that we need efficient drag to explain the very inefficient day-night re-circulation observed. We demonstrate that this drag could be due to Lorentz-force drag by a magnetic field as weak as 10 Gauss. Secondly, we show that a high metallicity is not required to match the large day-night temperature contrast. In fact, the effect of metallicity on the phase curve is different from cooler gas-giant counterparts, due to the high-temperature chemistry in WASP-18b's atmosphere. Additionally, we compare the current UHJ spectroscopic phase curves, WASP-18b and WASP-103b, and show that these two planets provide a consistent picture with remarkable similarities in their measured and inferred properties. However, key differences in these properties, such as their brightness offsets and radius anomalies, suggest that UHJ could be used to separate between competing theories for the inflation of gas-giant planets.

arXiv commentAccepted for publication in A&A

References in corpus (78)

• emcee: The MCMC Hammer
• The WASP Project and the SuperWASP Cameras
• batman: BAsic Transit Model cAlculatioN in Python
• Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
• A map of the day-night contrast of the extrasolar planet HD 189733b
• Detection of Thermal Emission from an Extrasolar Planet
• Atmospheric Circulation and Tides of "51Peg b-like" Planets
• Atmospheric circulation of hot Jupiters: Coupled radiative-dynamical general circulation model simulations of HD 189733b and HD 209458b
• Equatorial superrotation on tidally locked exoplanets
• The Kilodegree Extremely Little Telescope (KELT): A Small Robotic Telescope for Large-Area Synoptic Surveys
• The Statistics of Albedo and Heat Recirculation on Hot Exoplanets
• Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres over a Range of Metallicities and Temperatures
• 3D mixing in hot Jupiter atmospheres. I. application to the day/night cold trap in HD 209458b
• Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
• From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context
• 3.6 and 4.5 Micron Phase Curves and Evidence for Non-Equilibrium Chemistry in the Atmosphere of Extrasolar Planet HD 189733b
• Transitions in the cloud composition of hot Jupiters
• H- Opacity and Water Dissociation in the Dayside Atmosphere of the Very Hot Gas Giant WASP-18 b
• Inflating Hot Jupiters With Ohmic Dissipation
• Atmospheric Chemistry in Giant Planets, Brown Dwarfs, and Low-Mass Dwarf Stars II. Sulfur and Phosphorus
• Extremely Irradiated Hot Jupiters: Non-Oxide Inversions, H- Opacity, and Thermal Dissociation of Molecules
• The Influence of Non-Uniform Cloud Cover on Transit Transmission Spectra
• Global Climate and Atmospheric Composition of the Ultra-Hot Jupiter WASP-103b from HST and Spitzer Phase Curve Observations
• Magnetic Drag on Hot Jupiter Atmospheric Winds
• Inverting Phase Functions to Map Exoplanets
• Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences
• Thermal Phase Variations of WASP-12b: Defying Predictions
• Bayesian Analysis of Hot Jupiter Radius Anomalies: Evidence for Ohmic Dissipation?
• The hot-Jupiter Kepler-17b: discovery, obliquity from stroboscopic starspots, and atmospheric characterization
• Three Dimensional Modeling of Hot Jupiter Atmospheric Flows
• Atmospheric Heat Redistribution on Hot Jupiters
• The atmospheric circulation of a nine-hot Jupiter sample: Probing circulation and chemistry over a wide phase space
• Spitzer Phase Curve Constraints for WASP-43b at 3.6 and 4.5 microns
• Increased Heat Transport in Ultra-Hot Jupiter Atmospheres Through H${}_2$ Dissociation/Recombination
• The changing phases of extrasolar planet CoRoT-1b
• The Atmospheric Circulation of the Hot Jupiter WASP-43b: Comparing Three-Dimensional Models to Spectrophotometric Data
• The KELT-South Telescope
• Hot Nights on Extrasolar Planets: Mid-IR Phase Variations of Hot Jupiters
• Spitzer 3.6 micron and 4.5 micron full-orbit lightcurves of WASP-18
• 3.6 and 4.5 $\mu$m $Spitzer$ Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b
• Ohmic Dissipation in the Atmospheres of Hot Jupiters
• Magnetic Scaling Laws for the Atmospheres of Hot Giant Exoplanets
• Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences. II. Comparison with Observations
• The Peculiar Atmospheric Chemistry of KELT-9b
• Detection of the ellipsoidal and the relativistic beaming effects in the CoRoT-3 lightcurve
• Inflating and Deflating Hot Jupiters: Coupled Tidal and Thermal Evolution of Known Transiting Planets
• Magnetic Effects in Hot Jupiter Atmospheres
• Variability in the Atmosphere of the Hot Giant Planet HAT-P-7 b
• The Impact of Non-Uniform Thermal Structure on the Interpretation of Exoplanet Emission Spectra
• The Mechanical Greenhouse: Burial of Heat by Turbulence in Hot Jupiter Atmospheres
• Radiative Hydrodynamic Simulations of HD209458b: Temporal Variability
• 3.6 and 4.5 $\mu$m Phase Curves of the Highly-Irradiated Eccentric Hot Jupiter WASP-14b
• Spitzer Secondary Eclipses of WASP-18b
• Physical properties of the 0.94-day period transiting planetary system WASP-18
• TESS full orbital phase curve of the WASP-18b system
• A HST/WFC3 Thermal Emission Spectrum of the Hot Jupiter HAT-P-7b
• Evidence for a Dayside Thermal Inversion and High Metallicity for the Hot Jupiter WASP-18b
• A new Search for Carbon Monoxide Absorption in the Transmission Spectrum of the Extrasolar Planet HD 209458b
• Magnetically Controlled Circulation on Hot Extrasolar Planets
• Estimating the magnetic field strength in hot Jupiters
• Detection of a Westward Hotspot Offset in the Atmosphere of a Hot Gas Giant CoRoT-2b
• Ohmic Dissipation in the Interiors of Hot Jupiters
• Investigating hot-Jupiter inflated radii with hierarchical Bayesian modelling
• Sparkling nights and very hot days on WASP-18b: the formation of clouds and the emergence of an ionosphere
• The Atmospheric Circulation and Observable Properties of Non-Synchronously Rotating Hot Jupiters
• Circulation and Dissipation on Hot Jupiters
• The Very Low Albedo of WASP-12b From Spectral Eclipse Observations with $\text{Hubble}$
• Distorted, non-spherical transiting planets: impact on the transit depth and on the radius determination
• High-precision photometry by telescope defocussing. VII. The ultra-short period planet WASP-103
• On the Existence of Shocks in Irradiated Exoplanetary Atmospheres
• Shear-driven instabilities and shocks in the atmospheres of hot Jupiters
• The atmospheres of the hot-Jupiters Kepler-5b and Kepler-6b observed during occultations with Warm-Spitzer and Kepler
• Phase Offsets and the Energy Budgets of Hot Jupiters
• Thermodynamics of atmospheric circulation on hot Jupiters
• Revisiting the Energy Budget of WASP-43b: Enhanced day-night heat transport
• Shallow-water Magnetohydrodynamics for Westward Hotspots on Hot Jupiters
• On the heat redistribution of the hot transiting exoplanet WASP-18b
• The Role of Drag in the Energetics of Strongly Forced Exoplanet Atmospheres

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