A Hubble PanCET Study of HAT-P-11b: A Cloudy Neptune with a Low Atmospheric Metallicity

Abstract

We present the first comprehensive look at the $0.35-5$ $\mu$m transmission spectrum of the warm ($\sim 800$ K) Neptune HAT-P-11b derived from thirteen individual transits observed using the Hubble and Spitzer Space Telescopes. Along with the previously published molecular absorption feature in the $1.1-1.7$ $\mu$m bandpass, we detect a distinct absorption feature at 1.15 $\mu$m and a weak feature at 0.95 $\mu$m, indicating the presence of water and/or methane with a combined significance of 4.4 $\sigma$. We find that this planet's nearly flat optical transmission spectrum and attenuated near-infrared molecular absorption features are best-matched by models incorporating a high-altitude cloud layer. Atmospheric retrievals using the combined $0.35-1.7$ $\mu$m HST transmission spectrum yield strong constraints on atmospheric cloud-top pressure and metallicity, but we are unable to match the relatively shallow Spitzer transit depths without under-predicting the strength of the near-infrared molecular absorption bands. HAT-P-11b's HST transmission spectrum is well-matched by predictions from our microphysical cloud models. Both forward models and retrievals indicate that HAT-P-11b most likely has a relatively low atmospheric metallicity ($<4.6Z_{\odot }$ and $<86Z_{\odot }$ at the $2\sigma$ and $3\sigma$ levels respectively), in contrast to the expected trend based on the solar system planets. Our work also demonstrates that the wide wavelength coverage provided by the addition of the HST STIS data is critical for making these inferences.

arXiv commentAccepted for publication in AJ. 33 pages, 23 figures

References in corpus (104)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• batman: BAsic Transit Model cAlculatioN in Python
• The effects of snowlines on C/O in planetary atmospheres
• A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
• Models of Stars, Brown Dwarfs and Exoplanets
• Precipitating Condensation Clouds in Substellar Atmospheres
• Atmospheric circulation of hot Jupiters: Coupled radiative-dynamical general circulation model simulations of HD 189733b and HD 209458b
• Homogeneous studies of transiting extrasolar planets. IV. Thirty systems with space-based light curves
• Infrared Transmission Spectroscopy of the Exoplanets HD209458b and XO-1b Using the Wide Field Camera-3 on the Hubble Space Telescope
• Detection of atmospheric haze on an extrasolar planet: The 0.55 - 1.05 micron transmission spectrum of HD189733b with the Hubble Space Telescope
• Disequilibrium Carbon, Oxygen, and Nitrogen Chemistry in the Atmospheres of HD 189733b and HD 209458b
• C/O ratio as a Dimension for Characterizing Exoplanetary Atmospheres
• Neglected Clouds in T and Y Dwarf Atmospheres
• Separating gas-giant and ice-giant planets by halting pebble accretion
• Atmospheric Retrieval for Super-Earths: Uniquely Constraining the Atmospheric Composition with Transmission Spectroscopy
• The Mass-Metallicity Relation for Giant Planets
• Hubble Space Telescope Transmission Spectroscopy of the Exoplanet HD 189733b: High-altitude atmospheric haze in the optical and near-UV with STIS
• HAT-P-11b: A Super-Neptune Planet Transiting a Bright K Star in the Kepler Field
• A Precise Water Abundance Measurement for the Hot Jupiter WASP-43b
• The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets
• 3D mixing in hot Jupiter atmospheres. I. application to the day/night cold trap in HD 209458b
• 3.6 and 4.5 Micron Phase Curves and Evidence for Non-Equilibrium Chemistry in the Atmosphere of Extrasolar Planet HD 189733b
• A population study of gaseous exoplanets
• How to Distinguish between Cloudy Mini-Neptunes and Water/Volatile-Dominated Super-Earths
• Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b: 1. the Transit
• Compositional diversity in the atmospheres of hot Neptunes, with application to GJ 436b
• Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-Level Decorrelation
• Water Vapour Absorption in the Clear Atmosphere of an exo-Neptune
• A Correlation Between Stellar Activity and Hot Jupiter Emission Spectra
• Stellar Limb-Darkening Coefficients for CoRot and Kepler
• An ultrahot gas-giant exoplanet with a stratosphere
• Equilibrium chemistry down to 100 K - Impact of silicates and phyllosilicates on carbon/oxygen ratio
• Starspots, spin-orbit misalignment, and active latitudes in the HAT-P-11 exoplanetary system
• Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune-mass exoplanet
• A Sub-Neptune Exoplanet with a Low-Metallicity Methane-Depleted Atmosphere and Mie-Scattering Clouds
• HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering
• LDTk: Limb Darkening Toolkit
• Detection of H2O and evidence for TiO/VO in an ultra hot exoplanet atmosphere
• Transmission spectral properties of clouds for hot Jupiter exoplanets
• HAT-P-26b: A Neptune-Mass Exoplanet with a Well Constrained Heavy Element Abundance
• Hubble Space Telescope Near-IR Transmission Spectroscopy of the Super-Earth HD 97658b
• Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470 b
• HST hot Jupiter Transmission Spectral Survey: A detection of Na and strong optical absorption in HAT-P-1b
• HST/STIS Optical Transit Transmission Spectra of the hot-Jupiter HD209458b
• Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b
• The HST PanCET Program: Exospheric Mg II and Fe II in the Near-UV transmission spectrum of WASP-121b using Jitter Decorrelation
• The atmospheric circulation of a nine-hot Jupiter sample: Probing circulation and chemistry over a wide phase space
• The Oblique Orbit of the Super-Neptune HAT-P-11b
• The Complete transmission spectrum of WASP-39b with a precise water constraint
• An optical transmission spectrum for the ultra-hot Jupiter WASP-121b measured with the Hubble Space Telescope
• An absolute sodium abundance for a cloud-free 'hot Saturn' exoplanet
• Atmospheric Circulation of Eccentric Hot Neptune GJ436b
• Forward and Inverse Modeling of the Emission and Transmission Spectrum of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds
• The Transit Light Source Effect II: The Impact of Stellar Heterogeneity on Transmission Spectra of Planets Orbiting Broadly Sun-like Stars
• Planet formation with envelope enrichment: new insights on planetary diversity
• 3.6 and 4.5 $\mu$m $Spitzer$ Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b
• Trends in Atmospheric Properties of Neptune-Size Exoplanets
• High Metallicity and Non-equilibrium Chemistry in the Dayside Atmosphere of hot-Neptune GJ 436b
• HST hot-Jupiter transmission spectral survey: Haze in the atmosphere of WASP-6b
• Connecting Giant Planet Atmosphere and Interior Modeling: Constraints on Atmospheric Metal Enrichment
• A framework to combine low- and high-resolution spectroscopy for the atmospheres of transiting exoplanets
• Haze Production in the Atmospheres of super-Earths and mini-Neptunes: Insights from the Lab
• A new approach to analysing HST spatial scans: the transmission spectrum of HD 209458 b
• Forward modelling and retrievals with PLATON, a fast open source tool
• Formation of Silicate and Titanium Clouds on Hot Jupiters
• The Starspots of HAT-P-11: Evidence for a Solar-like Dynamo
• The Near-Infrared Transmission Spectra of TRAPPIST-1 Planets b, c, d, e, f, and g and Stellar Contamination in Multi-Epoch Transit Spectra
• Exo-Transmit: An Open-Source Code for Calculating Transmission Spectra for Exoplanet Atmospheres of Varied Composition
• Methane on Uranus: The case for a compact CH4 cloud layer at low latitudes and a severe CH4 depletion at high-latitudes based on re-analysis of Voyager occultation measurements and STIS spectroscopy
• Phase curves of WASP-33b and HD 149026b and a New Correlation Between Phase Curve Offset and Irradiation Temperature
• Water, High-Altitude Condensates, and Possible Methane Depletion in the Atmosphere of the Warm Super-Neptune WASP-107b
• Sedimentation Efficiency of Condensation Clouds in Substellar Atmospheres
• Exoplanet Clouds
• On Signatures of Clouds in Exoplanetary Transit Spectra
• A Possible Tilted Orbit of the Super-Neptune HAT-P-11b
• Global-mean Vertical Tracer Mixing in Planetary Atmospheres I: Theory and Fast-rotating Planets
• Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b
• A Physical Model-based Correction for Charge Traps in the Hubble Space Telescope's Wide Field Camera 3 Near-IR Detector and Applications to Transiting Exoplanets and Brown Dwarfs
• Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets
• Microphysics of KCl and ZnS Clouds on GJ 1214b
• HAT-P-11: Discovery of a Second Planet and a Clue to Understanding Exoplanet Obliquities
• The Emergent 1.1-1.7 Micron Spectrum of the Exoplanet CoRoT-2b as Measured Using the Hubble Space Telescope
• Constraints on the Microphysics of Pluto's Photochemical Haze from New Horizons Observations
• The atmospheric circulation of the super Earth GJ 1214b: Dependence on composition and metallicity
• Photochemical Haze Formation in the Atmospheres of super-Earths and mini-Neptunes
• The ExoMol Atlas of Molecular Opacities
• Global-mean Vertical Tracer Mixing in Planetary Atmospheres II: Tidally Locked Planets
• Laboratory Simulations of Haze Formation in the Atmospheres of super-Earths and mini-Neptunes: Particle Color and Size Distribution
• Kepler and Ground-based Transits of the Exo-Neptune HAT-P-11b
• An Observational Diagnostic for Distinguishing Between Clouds and Haze in Hot Exoplanet Atmospheres
• Spitzer Secondary Eclipse Observations of Five Cool Gas Giant Planets and Empirical Trends in Cool Planet Emission Spectra
• An HST/STIS Optical Transmission Spectrum of Warm Neptune GJ 436b
• HST PanCET program: A Cloudy Atmosphere for the promising JWST target WASP-101b
• Chemical Timescales in the Atmospheres of Highly Eccentric Exoplanets
• Hubble PanCET: An isothermal day-side atmosphere for the bloated gas-giant HAT-P-32Ab
• The HST PanCET Program: Hints of Na I & Evidence of a Cloudy Atmosphere for the Inflated Hot Jupiter WASP-52b
• Exoplanet Atmosphere Forecast: Observers Should Expect Spectroscopic Transmission Features to be Muted to 33%
• Chromospheric Activity of HAT-P-11: an Unusually Active Planet-Hosting K Star
• Discovery of the secondary eclipse of HAT-P-11 b
• The GTC exoplanet transit spectroscopy survey X. Stellar spots versus Rayleigh scattering: the case of HAT-P-11b
• Internal Structure of Giant and Icy Planets: Importance of Heavy Elements and Mixing

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• A Comparative Study of Atmospheric Chemistry with VULCAN
• Aerosols in Exoplanet Atmospheres
• PLATON II: New Capabilities And A Comprehensive Retrieval on HD 189733b Transit and Eclipse Data
• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• Deflating Super-Puffs: Impact of Photochemical Hazes on the Observed Mass-Radius Relationship of Low Mass Planets
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• A new perspective on interiors of ice-rich planets: Ice-rock mixture instead of ice on top of rock
• Grid of Pseudo-2D Chemistry Models for Tidally-Locked Exoplanets. I. The Role of Vertical and Horizontal Mixing
• Observability of signatures of transport-induced chemistry in clear atmospheres of hot gas giant exoplanets
• Seeing above the Clouds with High Resolution Spectroscopy
• WASP-127b transmission spectrum]{Abundance measurements of H${}_2$O and carbon-bearing species in the atmosphere of WASP-127b confirm its super-solar metallicity
• Dry or water world? How the water contents of inner sub-Neptunes constrain giant planet formation and the location of the water ice line
• Evidence for disequilibrium chemistry from vertical mixing in hot Jupiter atmospheres. A comprehensive survey of transiting close-in gas giant exoplanets with warm-Spitzer/IRAC
• Implementation of disequilibrium chemistry to spectral retrieval code ARCiS and application to sixteen exoplanet transmission spectra: Indication of disequilibrium chemistry for HD 209458b and WASP-39b
• The Impact of Mixing Treatments on Cloud Modelling in 3D Simulations of Hot Jupiters
• Transmission spectroscopy for the warm sub-Neptune HD3167c: evidence for molecular absorption and a possible high metallicity atmosphere
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• ARES IV: Probing the atmospheres of the two warm small planets HD 106315 c and HD 3167 c with the HST/WFC3 camera
• A Featureless Infrared Transmission Spectrum for the Super-Puff Planet Kepler-79d
• The GAPS Programme at TNG LV. Multiple molecular species in the atmosphere of HAT-P-11 b and review of the HAT-P-11 planetary system
• Cleaning our Hazy Lens: Exploring Trends in Transmission Spectra of Warm Exoplanets
• The role of clouds on the depletion of methane and water dominance in the transmission spectra of irradiated exoplanets
• The Exoplanet Perspective on Future Ice Giant Exploration
• Indications for very high metallicity and absence of methane for the eccentric exo-Saturn WASP-117b
• Spatially Resolved Modeling of Optical Albedos for a Sample of Six Hot Jupiters
• Clouds form on the hot Saturn JWST ERO target WASP-96b
• Tentative Evidence for Water Vapor in the Atmosphere of the Neptune-Size Exoplanet HD 106315 c
• The Hubble PanCET Program: A Metal-rich Atmosphere for the Inflated Hot Jupiter HAT-P-41b
• ACCESS: Confirmation of a Clear Atmosphere for WASP-96b and a Comparison of Light Curve Detrending Techniques
• Planet Mass and Metallicity: The Exoplanets and Solar System Connection
• Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere
• A Mirage or an Oasis? Water Vapor in the Atmosphere of the Warm Neptune TOI-674 b
• A Population Analysis of 20 Exoplanets Observed from the Optical to the Near-infrared Wavelengths with HST: Evidence for Widespread Stellar Contamination
• Strong NUV Refractory Absorption and Dissociated Water in the Hubble Transmission Spectrum of the Ultra Hot Jupiter KELT-20 b
• Comparing transit spectroscopy pipelines at the catalogue level: evidence for systematic differences
• HST Transmission Spectra of the Hot-Neptune HD 219666 b: Detection of Water and the Challenge of Constraining Both Water and Methane
• Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES${}^{+}$ observations
• Where does the simplified Stellar Contamination Model fail in Exoplanet Transmission Spectroscopy?
• Sub-Neptunes as Soot Factories: Deep Atmosphere Hydrocarbon Formation and Quenching as the Origin of Sub-Neptune Aerosol Trends
• JWST unveils a high mean molecular weight atmosphere for mini-Neptune TOI-1130b: Evidence for formation beyond the water ice line
• Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs