Thermal Phase Variations of WASP-12b: Defying Predictions

Abstract

[Abridged] We report Warm Spitzer full-orbit phase observations of WASP-12b at 3.6 and 4.5 micron. We are able to measure the transit depths, eclipse depths, thermal and ellipsoidal phase variations at both wavelengths. The large amplitude phase variations, combined with the planet's previously-measured day-side spectral energy distribution, is indicative of non-zero Bond albedo and very poor day-night heat redistribution. The transit depths in the mid-infrared indicate that the atmospheric opacity is greater at 3.6 than at 4.5 micron, in disagreement with model predictions, irrespective of C/O ratio. The secondary eclipse depths are consistent with previous studies. We do not detect ellipsoidal variations at 3.6 micron, but our parameter uncertainties -estimated via prayer-bead Monte Carlo- keep this non-detection consistent with model predictions. At 4.5 micron, on the other hand, we detect ellipsoidal variations that are much stronger than predicted. If interpreted as a geometric effect due to the planet's elongated shape, these variations imply a 3:2 ratio for the planet's longest:shortest axes and a relatively bright day-night terminator. If we instead presume that the 4.5 micron ellipsoidal variations are due to uncorrected systematic noise and we fix the amplitude of the variations to zero, the best fit 4.5 micron transit depth becomes commensurate with the 3.6 micron depth, within the uncertainties. The relative transit depths are then consistent with a Solar composition and short scale height at the terminator. Assuming zero ellipsoidal variations also yields a much deeper 4.5 micron eclipse depth, consistent with a Solar composition and modest temperature inversion. We suggest future observations that could distinguish between these two scenarios.

19 pages, 10 figures, ApJ in press. Improved discussion of gravity brightening

References in corpus (16)

• Detection of Thermal Emission from an Extrasolar Planet
• The effect of red noise on planetary transit detection
• Detection of atmospheric haze on an extrasolar planet: The 0.55 - 1.05 micron transmission spectrum of HD189733b with the Hubble Space Telescope
• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• Theoretical Spectral Models of the Planet HD 209458b with a Thermal Inversion and Water Emission Bands
• Multi-Wavelength Constraints on the Day-Night Circulation Patterns of HD 189733b
• The Very Low Albedo of an Extrasolar Planet: MOST Spacebased Photometry of HD 209458
• Inverting Phase Functions to Map Exoplanets
• Early UV Ingress in WASP-12b: Measuring Planetary Magnetic Fields
• Hot Nights on Extrasolar Planets: Mid-IR Phase Variations of Hot Jupiters
• A New 24 micron Phase Curve for upsilon Andromedae b
• The Transit Light Curve Project. III. Tres Transits of TrES-1
• A Sensitive Search for Variability in Late L Dwarfs: The Quest for Weather
• The shocking transit of WASP-12b: Modelling the observed early ingress in the near ultraviolet
• A Uniform Search for Secondary Eclipses of Hot Jupiters in Kepler Q2 Lightcurves
• Five New Transits of the Super-Neptune HD 149026

Cited by in corpus (142)

• C/O ratio as a Dimension for Characterizing Exoplanetary Atmospheres
• Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets
• Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
• 3.6 and 4.5 Micron Phase Curves and Evidence for Non-Equilibrium Chemistry in the Atmosphere of Extrasolar Planet HD 189733b
• KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star
• Chemical consequences of the C/O ratio on hot Jupiters: Examples from WASP-12b,CoRoT-2b, XO-1b, and HD 189733b
• Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-Level Decorrelation
• Extremely Irradiated Hot Jupiters: Non-Oxide Inversions, H- Opacity, and Thermal Dissociation of Molecules
• HST Spectral Mapping of L/T Transition Brown Dwarfs Reveals Cloud Thickness Variations
• The Influence of Non-Uniform Cloud Cover on Transit Transmission Spectra
• A Systematic Retrieval Analysis of Secondary Eclipse Spectra II: A Uniform Analysis of Eight Planets and Their C to O Ratios
• Exoplanetary Atmospheres - Chemistry, Formation Conditions, and Habitability
• HST hot Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b
• Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences
• Atmospheric Heat Redistribution on Hot Jupiters
• Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b
• The Apparently Decaying Orbit of WASP-12
• Atmospheric Dynamics of Hot Exoplanets
• Spitzer Phase Curve Constraints for WASP-43b at 3.6 and 4.5 microns
• Transmission Spectroscopy of the Hot-Jupiter WASP-12b from 0.7 to 5 microns
• The Orbit of WASP-12b is Decaying
• Increased Heat Transport in Ultra-Hot Jupiter Atmospheres Through H${}_2$ Dissociation/Recombination
• The 4.5 $\mu$m full-orbit phase curve of the hot Jupiter HD 209458b
• Homogeneous studies of transiting extrasolar planets. V. New results for 38 planets
• Characterizing Transiting Planet Atmospheres through 2025
• Exoplanet Transit Spectroscopy Using WFC3: WASP-12 b, WASP-17 b, and WASP-19 b
• H2O abundances in the atmospheres of three hot Jupiters
• Observations of Exoplanet Atmospheres
• Balancing the Energy Budget of Short-Period Giant Planets: Evidence for Reflective Clouds and Optical Absorbers
• Departure from the constant-period ephemeris for the transiting exoplanet WASP-12 b
• The Effects of Irradiation on Hot Jovian Atmospheres: Heat Redistribution and Energy Dissipation
• Atmospheric escape from HD 189733b observed in HI Lyman-alpha: detailed analysis of HST/STIS September 2011 observations
• The Atmospheric Circulation of Ultra-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
• Re-Evaluating WASP-12b: Strong Emission at 2.315 micron, Deeper Occultations, and an Isothermal Atmosphere
• The Habitability of Proxima Centauri b: II: Environmental States and Observational Discriminants
• Atmospheric Circulation of Hot Jupiters: Dayside-Nightside Temperature Differences. II. Comparison with Observations
• Probing the extreme planetary atmosphere of WASP-12b
• Magnetic Effects in Hot Jupiter Atmospheres
• Aerosols in Exoplanet Atmospheres
• Spitzer observations of the thermal emission from WASP-43b
• Deciphering the Atmospheric Composition of WASP-12b: A Comprehensive Analysis of its Dayside Emission
• Climate of an Ultra hot Jupiter: Spectroscopic phase curve of WASP-18b with HST/WFC3
• Magnetohydrodynamic Simulations of the Atmosphere of HD 209458b
• Ground-based near-UV observations of 15 transiting exoplanets: Constraints on their atmospheres and no evidence for asymmetrical transits
• Spectra as Windows into Exoplanet Atmospheres
• 3.6 and 4.5 $\mu$m Phase Curves of the Highly-Irradiated Eccentric Hot Jupiter WASP-14b
• Phase curves of WASP-33b and HD 149026b and a New Correlation Between Phase Curve Offset and Irradiation Temperature
• TESS Transit Timing of Hundreds of Hot Jupiters
• Spitzer Phase Curves of KELT-1b and the Signatures of Nightside Clouds in Thermal Phase Observations
• Exoplanet Clouds
• Features in the Broadband Eclipse Spectra of Exoplanets: Signal or Noise?
• Highlights in the Study of Exoplanet Atmospheres
• Studying atmosphere-dominated hot Jupiter Kepler phase curves: Evidence that inhomogeneous atmospheric reflection is common
• A Semi-Analytical Model of Visible-Wavelength Phase Curves of Exoplanets and Applications to Kepler-7 b and Kepler-10 b
• The astrophysics of visible-light orbital phase curves in the space age
• Five key exoplanet questions answered via the analysis of 25 hot Jupiter atmospheres in eclipse
• Vertical Tracer Mixing in Hot Jupiter Atmospheres
• The continuing search for evidence of tidal orbital decay of hot Jupiters
• TEA: A Code for Calculating Thermochemical Equilibrium Abundances
• WASP-8b: Characterization of a Cool and Eccentric Exoplanet with Spitzer
• Deciphering thermal phase curves of dry, tidally locked terrestrial planets
• Uniformly hot nightside temperatures on short-period gas giants
• Detection of a Westward Hotspot Offset in the Atmosphere of a Hot Gas Giant CoRoT-2b
• Thermal Processes Governing Hot-Jupiter Radii
• A Case for an Atmosphere on Super-Earth 55 Cancri e
• Decaying Orbit of the Hot Jupiter WASP-12b: Confirmation with TESS Observations
• Infrared Eclipses of the Strongly Irradiated Planet WASP-33b, and Oscillations of its Host Star
• Lightcurves of Stars & Exoplanets: Estimating Inclination, Obliquity, and Albedo
• Mass Loss from the Exoplanet WASP-12b Inferred from $\text{Spitzer}$ Phase Curves
• Near-infrared Thermal Emission Detections of a number of hot Jupiters and the Systematics of Ground-based Near-infrared Photometry
• Atmospheric Retrieval of Exoplanets
• A transition between the hot and the ultra-hot Jupiter atmospheres
• Systematic Phase Curve Study of Known Transiting Systems from Year 1 of the TESS Mission
• The Atmospheric Circulation and Observable Properties of Non-Synchronously Rotating Hot Jupiters
• A Comprehensive Reanalysis of $\text{Spitzer}$'s 4.5 $\mu$m Phase Curves, and the Phase Variations of the Ultra-hot Jupiters MASCARA-1b and KELT-16b
• The Very Low Albedo of WASP-12b From Spectral Eclipse Observations with $\text{Hubble}$
• Identifying new opportunities for exoplanet characterisation at high spectral resolution
• Visible-light Phase Curves from the Second Year of the TESS Primary Mission
• Warm Spitzer Photometry of Three Hot Jupiters: HAT-P-3b, HAT-P-4b and HAT-P-12b
• Multi-site campaign for transit timing variations of WASP-12 b: possible detection of a long-period signal of planetary origin
• Phase Offsets and the Energy Budgets of Hot Jupiters
• No hydrogen exosphere detected around the super-Earth HD97658 b
• TESS Revisits WASP-12: Updated Orbital Decay Rate and Constraints on Atmospheric Variability
• Detecting the spin-orbit misalignment of the super-Earth 55 Cnc e
• Exoplanet phase curves: observations and theory
• Chemical variation with altitude and longitude on exo-Neptunes: Predictions for Ariel phase-curve observations
• The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs
• Hubble PanCET: An isothermal day-side atmosphere for the bloated gas-giant HAT-P-32Ab
• The EVIL-MC Model for Ellipsoidal Variations of Planet-Hosting Stars and Applications to the HAT-P-7 System
• CO or no CO? Narrowing the CO abundance constraint and recovering the H2O detection in the atmosphere of WASP-127 b using SPIRou
• A JWST NIRSpec Phase Curve for WASP-121b: Dayside Emission Strongest Eastward of the Substellar Point and Nightside Conditions Conducive to Cloud Formation
• Obliquity Tides May Drive WASP-12b's Rapid Orbital Decay
• A More Informative Map: Inverting Thermal Orbital Phase and Eclipse Lightcurves of Exoplanets
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• The hottest hot Jupiters may host Atmospheric Dynamos
• Transmission photometry of WASP-12b: simultaneous measurement of the planetary radius in three bands
• A New Analysis of 8 Spitzer Phase Curves and Hot Jupiter Population Trends: Qatar-1b, Qatar-2b, WASP-52b, WASP-34b, and WASP-140b
• JWST Transit Spectra I: Exploring Potential Biases and Opportunities in Retrievals of Tidally-locked Hot Jupiters with Clouds and Hazes
• Pseudo-2D Modelling of Heat Redistribution Through H${}_2$ Thermal Dissociation/Recombination: Consequences for Ultra-Hot Jupiters
• Wavelength Does Not Equal Pressure: Vertical Contribution Functions and their Implications for Mapping Hot Jupiters
• Hot Jupiter Diversity and the Onset of TiO/VO Revealed by a Large Grid of Non-Grey Global Circulation Models
• ULTRACAM z'-band Detection of the Secondary Eclipse of WASP-12b
• The GAPS Programme with HARPS-N at TNG XVII. Line profile indicators and kernel regression as diagnostics of radial-velocity variations due to stellar activity in solar-like stars
• Phase curve pollution of exoplanet transmission spectra
• On the heat redistribution of the hot transiting exoplanet WASP-18b
• Integrating light-curve and atmospheric modelling of transiting exoplanets
• Spitzer IRAC Sparsely Sampled Phase Curve of the Exoplanet WASP-14b
• First Light of Engineered Diffusers at the Nordic Optical Telescope Reveal Time Variability in the Optical Eclipse Depth of WASP-12b
• Future Direct Spectroscopic Detection of Hot Jupiters with IGRINS
• Repeatability of Spitzer/IRAC exoplanetary eclipses with Independent Component Analysis
• A new approach to spectroscopic phase curves: The emission spectrum of WASP-12b observed in quadrature with HST/WFC3
• A survey of exoplanet phase curves with Ariel
• Storms or Systematics? The changing secondary eclipse depth of WASP-12b
• Transmission strings: a technique for spatially mapping exoplanet atmospheres around their terminators
• Distinguishing Between Stellar and Planetary Companions With Phase Monitoring
• Constraining Exoplanet Metallicities and Aerosols with ARIEL: An Independent Study by the Contribution to ARIEL Spectroscopy of Exoplanets (CASE) Team
• Observational Consequences of Shallow-water Magnetohydrodynamics on Hot Jupiters
• Mapping Exoplanets
• Signatures of Obliquity in Thermal Phase Curves of Hot Jupiters
• A blind method to detrend instrumental systematics in exoplanetary light-curves
• Coupled Day-Night Models of Exoplanetary Atmospheres
• Mapping the pressure-dependent day-night temperature contrast of a strongly irradiated atmosphere with HST spectroscopic phase curve
• Exoplanetary Geophysics -- An Emerging Discipline
• Thermal Phase Curves of XO-3b: an Eccentric Hot Jupiter at the Deuterium Burning Limit
• Hot exoplanetary atmospheres in 3D
• Phase curve and variability analysis of WASP-12b using TESS photometry
• Reassessing Exoplanet Light Curves with a Thermal Model
• Knot a Bad Idea: Testing BLISS Mapping for Spitzer Space Telescope Photometry
• On the Dayside Atmosphere of WASP-12b
• Hotter Than Expected: HST/WFC3 Phase-resolved Spectroscopy of a Rare Irradiated Brown Dwarf with Strong Internal Heat Flux
• Planetary influences on photometric variation of the extreme helium subdwarf KIC10449976
• Under the magnifying glass: A combined 3D model applied to cloudy warm Saturn type exoplanets around M-dwarfs
• Lessons from Hubble and Spitzer: 1D Self-Consistent Model Grids for 19 Hot Jupiter Emission Spectra
• Illusion and Reality in the Atmospheres of Exoplanets
• Refined Ephemeris for Four Hot Jupiters using Ground-Based and TESS Observations
• Atmospheric characterization of hot Jupiters using hierarchical models of Spitzer observations
• Null transit detections of 68 radial velocity exoplanets observed by TESS
• The Observational Effects and Signatures of Tidally Distorted Solid Exoplanets
• Re-evaluating Hot Jupiter WASP-12b: An Update
• Precise Constraints on the Energy Budget of WASP-121 b from its JWST NIRISS/SOSS Phase Curve