Spitzer Transit and Secondary Eclipse Photometry of GJ 436b

Abstract

We report the results of infrared (8 micron) transit and secondary eclipse photometry of the hot Neptune exoplanet, GJ436b using Spitzer. The nearly photon-limited precision of these data allow us to measure an improved radius for the planet, and to detect the secondary eclipse. The transit (centered at HJD = 2454280.78149 +/-0.00016) shows the flat-bottomed shape typical of infrared transits, and it precisely defines the planet-to-star radius ratio (0.0839 +/-0.0005), independent of the stellar properties. However, we obtain the planetary radius, as well as the stellar mass and radius, by fitting to the transit curve simultaneously with an empirical mass-radius relation for M-dwarfs (M=R). We find Rs=Ms=0.47 +/-0.02 in solar units, and Rp=27,600 +/-1170 km (4.33 +/-0.18 Earth radii). This radius significantly exceeds the radius of a naked ocean planet, and requires a gasesous hydrogen-helium envelope. The secondary eclipse occurs at phase 0.587 +/-0.005, proving a significant orbital eccentricity (e=0.15 +/-0.012). The amplitude of the eclipse (5.7 +/-0.8e-4) indicates a brightness temperature for the planet of T=712 +/-36K. If this is indicative of the planet's physical temperature, it suggests the occurrence of tidal heating in the planet. An uncharacterized second planet likely provides ongoing gravitational perturbations, to maintain GJ436b's orbit eccentricity over long time scales.

15 pages, 2 figures, submitted to ApJ Letters

References in corpus (17)

• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• Analytic Lightcurves for Planetary Transit Searches
• Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits
• A map of the day-night contrast of the extrasolar planet HD 189733b
• Detection of Thermal Emission from an Extrasolar Planet
• Infrared radiation from an extrasolar planet
• HST Time-Series Photometry of the Transiting Planet of HD 209458
• A Neptune-Mass Planet Orbiting the Nearby M Dwarf GJ 436
• Detection of transits of the nearby hot Neptune GJ 436 b
• Strong Infrared Emission from the Extrasolar Planet HD189733b
• The Transit Light Curve Project. V. System Parameters and Stellar Rotation Period of HD 189733
• Accurate Spitzer infrared radius measurement for the hot Neptune GJ 436b
• Masses and Radii of Low-Mass Stars: Theory versus Observations
• The M Dwarf GJ 436 and its Neptune-Mass Planet
• Tidal dissipation within hot Jupiters: a new appraisal
• Metallicities of M Dwarf Planet Hosts from Spectral Synthesis
• A Spitzer Infrared Radius for the Transiting Extrasolar Planet HD209458b

Cited by in corpus (132)

• A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres
• The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample
• Improved parameters for extrasolar transiting planets
• The 3.6-8.0 Micron Broadband Emission Spectrum of HD 209458b: Evidence for an Atmospheric Temperature Inversion
• Exoplanet Atmospheres
• Design Considerations for a Ground-based Transit Search for Habitable Planets Orbiting M dwarfs
• HAT-P-11b: A Super-Neptune Planet Transiting a Bright K Star in the Kepler Field
• Tidal Evolution of Close-in Extra-Solar Planets
• The Statistics of Albedo and Heat Recirculation on Hot Exoplanets
• Homogeneous studies of transiting extrasolar planets. I. Light curve analyses
• A Framework for Quantifying the Degeneracies of Exoplanet Interior Compositions
• Structure and evolution of super-Earth to super-Jupiter exoplanets: I. heavy element enrichment in the interior
• Possible thermochemical disequilibrium in the atmosphere of the exoplanet GJ 436b
• The Broadband Infrared Emission Spectrum of the Exoplanet HD 189733b
• Compositional diversity in the atmospheres of hot Neptunes, with application to GJ 436b
• 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
• Lyman-$\alpha$ Transit Spectroscopy and the Neutral Hydrogen Tail of the Hot Neptune GJ436b
• The Atmospheric Signatures of Super-Earths: How to Distinguish Between Hydrogen-Rich and Hydrogen-Poor Atmospheres
• Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres
• Search for Carbon Monoxide in the atmosphere of the Transiting Exoplanet HD189733b
• Tidally Heated Terrestrial Exoplanets: Viscoelastic Response Models
• Three Dimensional Modeling of Hot Jupiter Atmospheric Flows
• Analytic Approximations for Transit Light Curve Observables, Uncertainties, and Covariances
• N-body simulations of planetary accretion around M dwarf stars
• XO-3b: A Massive Planet in an Eccentric Orbit Transiting an F5V Star
• Observable Consequences of Planet Formation Models in Systems with Close-in Terrestrial Planets
• Atmospheric Dynamics of Short-period Extra Solar Gas Giant Planets I: Dependence of Night-Side Temperature on Opacity
• Atmospheric Circulation of Eccentric Hot Neptune GJ436b
• How eccentric orbital solutions can hide planetary systems in 2:1 resonant orbits
• Forward and Inverse Modeling of the Emission and Transmission Spectrum of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds
• The 8 Micron Phase Variation of the Hot Saturn HD 149026b
• The Nature of the Atmosphere of the Transiting Super-Earth GJ 1214b
• Homogeneous studies of transiting extrasolar planets. II. Physical properties
• A Model for Thermal Phase Variations of Circular and Eccentric Exoplanets
• Thermochemistry and Photochemistry in Cooler Hydrogen Dominated Extrasolar Planets: The Case of GJ436b
• High Metallicity and Non-equilibrium Chemistry in the Dayside Atmosphere of hot-Neptune GJ 436b
• A Spitzer Transmission Spectrum for the Exoplanet GJ 436b, Evidence for Stellar Variability, and Constraints on Dayside Flux Variations
• A global analysis of Spitzer and new HARPS data confirms the loneliness and metal-richness of GJ 436 b
• Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths
• A uniform analysis of HD209458b Spitzer/IRAC lightcurves with Gaussian process models
• Observational Evidence for Tidal Interaction in Close Binary Systems
• Tides and the Evolution of Planetary Habitability
• The Transiting Exoplanet Community Early Release Science Program for JWST
• Aerosols in Exoplanet Atmospheres
• Thermal Emission of Exoplanet XO-1b
• Studying the atmosphere of the exoplanet HAT-P-7b via secondary eclipse measurements with EPOXI, Spitzer and Kepler
• Detection of a Temperature Inversion in the Broadband Infrared Emission Spectrum of TrES-4
• The transiting exoplanet host star GJ 436: a test of stellar evolution models in the lower main sequence, and revised planetary parameters
• Ground-based near-UV observations of 15 transiting exoplanets: Constraints on their atmospheres and no evidence for asymmetrical transits
• Observational constraints on tidal effects using orbital eccentricities
• Methane in the atmosphere of the transiting hot Neptune GJ436b?
• The GJ 436 System: Directly Determined Astrophysical Parameters of an M-Dwarf and Implications for the Transiting Hot Neptune
• Three-dimensional atmospheric circulation of hot Jupiters on highly eccentric orbits
• Extrasolar Planet Transits Observed at Kitt Peak National Observatory
• Features in the Broadband Eclipse Spectra of Exoplanets: Signal or Noise?
• Optical Albedo Theory of Strongly-Irradiated Giant Planets: The Case of HD 209458b
• From planetesimals to planets: volatile molecules
• Review: Far-Infrared Instrumentation and Technology Development for the Next Decade
• Transiting planets - lightcurve analysis for eccentric orbits
• Four Sub-Saturns with Dissimilar Densities: Windows into Planetary Cores and Envelopes
• A ~5 M_earth Super-Earth Orbiting GJ 436?: The Power of Near-Grazing Transits
• HATS-1b: The First Transiting Planet Discovered by the HATSouth Survey
• WASP-8b: Characterization of a Cool and Eccentric Exoplanet with Spitzer
• Transmission Spectra of Transiting Planet Atmospheres: Model Validation and Simulations of the Hot Neptune GJ 436b for JWST
• An Independent Analysis of Kepler-4b through Kepler-8b
• Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits
• Empirical Constraints on Trojan Companions and Orbital Eccentricities in 25 Transiting Exoplanetary Systems
• Spitzer IRAC Secondary Eclipse Photometry of the Transiting Extrasolar Planet HAT-P-1b
• The Broadband Infrared Emission Spectrum of the Exoplanet TrES-3
• Transiting Exoplanets with JWST
• The puzzling chemical composition of GJ 436b's atmosphere: influence of tidal heating on the chemistry
• Limits to the planet candidate GJ 436c
• Transit infrared spectroscopy of the hot neptune around GJ 436 with the Hubble Space Telescope
• A Search for Additional Planets in the NASA EPOXI Observations of the Exoplanet System GJ 436
• Bright Opportunities for Atmospheric Characterization of Small Planets: Masses and Radii of K2-3 b, c, d and GJ3470 b from Radial Velocity Measurements and Spitzer Transits
• Distorted, non-spherical transiting planets: impact on the transit depth and on the radius determination
• Detection of Planetary Emission from the Exoplanet TrES-2 using Spitzer /IRAC
• A Hubble Space Telescope transit light curve for GJ436b
• Two nearby sub-Earth-sized exoplanet candidates in the GJ 436 system
• Non-Detection of Polarized, Scattered Light from the HD 189733b Hot Jupiter
• Secondary eclipse observations for seven hot-Jupiters from the Anglo-Australian Telescope
• A Quasi-Stationary Solution to Gliese 436b's Eccentricity
• ExoClock project II: A large-scale integrated study with 180 updated exoplanet ephemerides
• The HD 40307 Planetary System: Super-Earths or Mini-Neptunes?
• The Limits of the Primitive Equations of Dynamics for Warm, Slowly Rotating Small Neptunes and Super Earths
• Revisiting Spitzer transit observations with Independent Component Analysis: new results for the GJ436 system
• Transit spectrophotometry of the exoplanet HD189733b. II. New Spitzer observations at 3.6 microns
• Planetpol polarimetry of the exoplanet systems 55 Cnc and tau Boo
• Observational Consequences of the Recently Proposed Super-Earth Orbiting GJ436
• A Precise Estimate of the Radius of the Exoplanet HD 149026b from Spitzer Photometry
• The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs
• Mid-Infrared Variability of protostars in IC 1396A
• Interior structure models of GJ 436b
• Theoretical Radii of Extrasolar Giant Planets: the Cases of TrES-4, XO-3b, and HAT-P-1b
• A Hubble Space Telescope Search for a Sub-Earth-Sized Exoplanet in the GJ 436 System
• From cold to hot irradiated gaseous exoplanets: Toward an observation-based classification scheme
• Coupled Thermal and Compositional Evolution of Photo Evaporating Planet Envelopes
• Transit Observations of the WASP-10 System
• Models of Neptune-Mass Exoplanets: Emergent Fluxes and Albedos
• HAT-P-24b: An inflated hot-Jupiter on a 3.36d period transiting a hot, metal-poor star
• Colour-magnitude diagrams of transiting Exoplanets - II. A larger sample from photometric distances
• New Observations and a Possible Detection of Parameter Variations in the Transits of Gliese 436b
• On Signatures of Atmospheric Features in Thermal Phase Curves of Hot Jupiters
• A Revised Orbital Ephemeris for HAT-P-9b
• Detection of period variations in extrasolar transiting planet OGLE-TR-111b
• Dynamical evolution of the Gliese 436 planetary system - Kozai migration as a potential source for Gliese 436b's eccentricity
• High Cadence Near Infrared Timing Observations of Extrasolar Planets: I. GJ 436b and XO-1b
• A temperature inversion in WASP-33b? Large Binocular Telescope occultation data confirm significant thermal flux at short wavelengths
• Helium Enhanced Planets Along the Upper Edge of the Radius Valley
• Photometric Follow-up Observations of the Transiting Neptune-Mass Planet GJ 436b
• The Spitzer search for the transits of HARPS low-mass planets - I. No transit for the super-Earth HD 40307b
• On the possibility of detecting extrasolar planets' atmospheres with the Rossiter-McLaughlin-effect
• The TRAPPIST-1 JWST Community Initiative
• The SOPHIE search for northern extrasolar planets XV. A Warm Neptune around the M-dwarf Gl378
• Characterization of Exoplanets: Secondary Eclipses
• Estimating dayside effective temperatures of hot Jupiters and associated uncertainties through Gaussian process regression
• Detection and Characterization of Extrasolar Planets through Doppler Spectroscopy
• The Next Generation Transit Survey - Prototyping Phase
• New constraints on the HR 8799 planetary system from mid-infrared direct imaging
• A New Method for Characterizing Very-Low-Mass Companions with Low Resolution Near-Infrared Spectroscopy
• Measuring accurate transit parameters
• Reassessing Exoplanet Light Curves with a Thermal Model
• Spitzer 24-micron Time-Series Observations of the Eclipsing M-dwarf Binary GU Bootis
• Mysterious non-detection of HeI (23S) transit absorption of GJ436b
• An educated search for transiting habitable planets. Targetting M dwarfs with known transiting planets
• Eccentricity modulation of a close-in planet by a companion - application to GJ 436 system
• Emergent Exoplanet Flux: Review of the Spitzer Results
• The case for a close-in perturber to GJ 436 b
• A Mid-Infrared Search for Substellar Companions of Nearby Planet-Host Stars
• The Transits of Extrasolar Planets with Moons