Cleaning our Hazy Lens: Exploring Trends in Transmission Spectra of Warm Exoplanets

Abstract

Relatively little is understood about the atmospheric composition of temperate to warm exoplanets (equilibrium temperature $T_{\mathrm{eq}}<$ 1000 K), as many of them are found to have uncharacteristically flat transmission spectra. Their flattened spectra are likely due to atmospheric opacity sources such as planet-wide photochemical hazes and condensation clouds. We compile the transmission spectra of 25 warm exoplanets previously observed by the Hubble Space Telescope and quantify the haziness of each exoplanet using a normalized amplitude of the water absorption feature ($A_{\mathrm{H}}$). By examining the relationships between $A_{\mathrm{H}}$ and various planetary and stellar forcing parameters, we endeavor to find correlations of haziness associated with planetary properties. We adopt new statistical correlation tests that are more suitable for the small, non-normally distributed warm exoplanet sample. Our analysis shows that none of the parameters hold statistically significant correlation with $A_{\mathrm{H}}$ ($p\le 0.01$) with the addition of new exoplanet data, including the previously identified linear trends between $A_{\mathrm{H}}$ and $T_{\mathrm{eq}}$ or hydrogen-helium envelope mass fraction (f${}_{\mathrm{HHe}}$). This suggests that haziness in warm exoplanets is not simply controlled by any single planetary/stellar parameter. Among all the parameters we investigated, planet gravity ($g_{\mathrm{p}}$), atmospheric scale height ($H$), planet density (${\rho }_{\mathrm{p}}$), orbital eccentricity ($e$), and age of the star ($t_{\mathrm{age}}$) hold tentative correlations with $A_{\mathrm{H}}$. Specifically, lower $H$, higher $g_{\mathrm{p}}$, ${\rho }_{\mathrm{p}}$, $e$, or $t_{\mathrm{age}}$ may lead to clearer atmospheres. We still need more observations and laboratory experiments to fully understand the complex physics and chemistry involved in creating hazy warm exoplanets.

arXiv comment29 pages, 6 figures, 6 tables, accepted by ApJ

References in corpus (152)

• The Transiting Exoplanet Survey Satellite
• The K2 Mission: Characterization and Early results
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler
• The false positive rate of Kepler and the occurrence of planets
• The Revised TESS Input Catalog and Candidate Target List
• A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
• Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
• Evolution of the Solar Activity over Time and Effects on Planetary Atmospheres: I. High-energy Irradiances (1-1700 A)
• Prevalence of Earth-size planets orbiting Sun-like stars
• A super-Earth transiting a nearby low-mass star
• Kepler planets: a tale of evaporation
• The evaporation valley in the Kepler planets
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• Detection of Thermal Emission from an Extrasolar Planet
• Growth Model Interpretation of Planet Size Distribution
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog With Measured Completeness and Reliability Based on Data Release 25
• Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres
• HAT-P-11b: A Super-Neptune Planet Transiting a Bright K Star in the Kepler Field
• The MUSCLES Treasury Survey I: Motivation and Overview
• The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets
• Titan's Atmosphere and Climate
• Metallicity and Temperature Indicators in M dwarf K band Spectra: Testing New & Updated Calibrations With Observations of 133 Solar Neighborhood M dwarfs
• The GAPS Programme with HARPS-N@TNG XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets
• A temperate rocky super-Earth transiting a nearby cool star
• A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b
• A population study of gaseous exoplanets
• A Framework for Characterizing the Atmospheres of Low-Mass Low-Density Transiting Planets
• The Effect of Condensates on the Characterization of Transiting Planet Atmospheres with Transmission Spectroscopy
• Water Vapor and Clouds on the Habitable-Zone Sub-Neptune Exoplanet K2-18b
• Breeding Super-Earths and Birthing Super-Puffs in Transitional Disks
• Water Vapour Absorption in the Clear Atmosphere of an exo-Neptune
• Water vapour in the atmosphere of the habitable-zone eight Earth-mass planet K2-18 b
• The Ultraviolet Radiation Environment Around M dwarf Exoplanet Host Stars
• Thermal Emission and Albedo Spectra of Super Earths with Flat Transmission Spectra
• Rotation periods of 12 000 main-sequence Kepler stars: Dependence on stellar spectral type and comparison with v sin i observations
• A Plateau in the Planet Population Below Twice the Size of Earth
• A Sub-Neptune Exoplanet with a Low-Metallicity Methane-Depleted Atmosphere and Mie-Scattering Clouds
• A rocky planet transiting a nearby low-mass star
• Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1
• Stellar Rotation Periods of the Kepler Objects of Interest: A Dearth of Close-in Planets around Fast Rotators
• Aerosol Composition of Hot Giant Exoplanets Dominated by Silicates and Hydrocarbon Hazes
• Quantitatively Assessing the Role of Clouds in the Transmission Spectrum of GJ 1214b
• A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c
• 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
• The Intrinsic Extreme Ultraviolet Fluxes of F5 V to M5 V Stars
• Thermal evolution and structure models of the transiting super-Earth GJ 1214b
• The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars
• HAT-P-12b: A Low-Density Sub-Saturn Mass Planet Transiting a Metal-Poor K Dwarf
• Forward and Inverse Modeling of the Emission and Transmission Spectrum of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds
• Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars
• Three sub-Jupiter-mass planets: WASP-69b & WASP-84b transit active K dwarfs and WASP-70Ab transits the evolved primary of a G4+K3 binary
• Planet formation with envelope enrichment: new insights on planetary diversity
• The theory of transmission spectra revisited: a semi-analytical method for interpreting WFC3 data and an unresolved challenge
• Quantifying and Predicting the Presence of Clouds in Exoplanet Atmospheres
• Trends in Atmospheric Properties of Neptune-Size Exoplanets
• HAT-P-26b: A Low-Density Neptune-Mass Planet Transiting a K Star
• A global analysis of Spitzer and new HARPS data confirms the loneliness and metal-richness of GJ 436 b
• Connecting Giant Planet Atmosphere and Interior Modeling: Constraints on Atmospheric Metal Enrichment
• Haze Production in the Atmospheres of super-Earths and mini-Neptunes: Insights from the Lab
• Searching the Entirety of Kepler Data. II. Occurrence Rate Estimates for FGK Stars
• Planetary evolution with atmospheric photoevaporation I. Analytical derivation and numerical study of the evaporation valley and transition from super-Earths to sub-Neptunes
• 3D modeling of GJ1214b's atmosphere: formation of inhomogeneous high clouds and observational implications
• Mass-loss rates for transiting exoplanets
• Aerosols in Exoplanet Atmospheres
• Spitzer Observations Confirm and Rescue the Habitable-Zone Super-Earth K2-18b for Future Characterization
• The Near-Infrared Transmission Spectra of TRAPPIST-1 Planets b, c, d, e, f, and g and Stellar Contamination in Multi-Epoch Transit Spectra
• The transiting exoplanet host star GJ 436: a test of stellar evolution models in the lower main sequence, and revised planetary parameters
• Theoretical transmission spectra of exoplanet atmospheres with hydrocarbon haze: Effect of creation, growth, and settling of haze particles. I. Model description and first results
• The Featureless Transmission Spectra of Two Super-Puff Planets
• The discoveries of WASP-91b, WASP-105b and WASP-107b: two warm Jupiters and a planet in the transition region between ice giants and gas giants
• WASP-80b: a gas giant transiting a cool dwarf
• WASP-80b has a dayside within the T-dwarf range
• Computing Intrinsic Lyman-alpha Fluxes of F5 V to M5 V Stars
• Theoretical Transit Spectra for GJ 1214b and Other "Super-Earths"
• KOI-152's Low Density Planets
• CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series
• Water, High-Altitude Condensates, and Possible Methane Depletion in the Atmosphere of the Warm Super-Neptune WASP-107b
• Transit Signatures of Inhomogeneous Clouds on Hot Jupiters: Insights From Microphysical Cloud Modeling
• A second terrestrial planet orbiting the nearby M dwarf LHS 1140
• HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars
• WASP-107b's density is even lower: a case study for the physics of planetary gas envelope accretion and orbital migration
• Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets
• Microphysics of KCl and ZnS Clouds on GJ 1214b
• The GAPS Programme with HARPS-N at TNG XVI: Measurement of the Rossiter-McLaughlin effect of the transiting planetary systems HAT-P-3, HAT-P-12, HAT-P-22, WASP-39 and WASP-60
• Three's Company: An additional non-transiting super-Earth in the bright HD 3167 system, and masses for all three planets
• The CARMENES search for exoplanets around M dwarfs: A low-mass planet in the temperate zone of the nearby K2-18
• HAT-P-11: Discovery of a Second Planet and a Clue to Understanding Exoplanet Obliquities
• Far-Ultraviolet Activity Levels of F, G, K, and M dwarf Exoplanet Host Stars
• A He I upper atmosphere around the warm Neptune GJ 3470b
• Deflating Super-Puffs: Impact of Photochemical Hazes on the Observed Mass-Radius Relationship of Low Mass Planets
• A scenario of planet erosion by coronal radiation
• A unique hot Jupiter spectral sequence with evidence for compositional diversity
• HAT-P-17b,c: A Transiting, Eccentric, Hot Saturn and a Long-period, Cold Jupiter
• On the effects of clouds and hazes in the atmospheres of hot Jupiters: semi-analytical temperature-pressure profiles
• WASP-29b: A Saturn-sized transiting exoplanet
• Living with a Red Dwarf: Rotation and X-ray and Ultraviolet Properties of the Halo Population Kapteyn's Star
• Photochemical Haze Formation in the Atmospheres of super-Earths and mini-Neptunes
• Confirmation of the radial velocity super-Earth K2-18c with HARPS and CARMENES
• Radial velocity follow-up of GJ1132 with HARPS. A precise mass for planet 'b' and the discovery of a second planet
• Warm Ice Giant GJ 3470b. II Revised Planetary and Stellar Parameters from Optical to Near-infrared Transit Photometry
• Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b
• Identifying the "true" radius of the hot sub-Neptune CoRoT-24b by mass loss modelling
• Super-Rayleigh Slopes in Transmission Spectra of Exoplanets Generated by Photochemical Haze
• Dusty outflows in planetary atmospheres: Understanding "super-puffs" and transmission spectra of sub-Neptunes
• Updated Parameters and a New Transmission Spectrum of HD 97658b
• Laboratory Simulations of Haze Formation in the Atmospheres of super-Earths and mini-Neptunes: Particle Color and Size Distribution
• Detection of an Atmosphere on a Rocky Exoplanet
• Kepler and Ground-based Transits of the Exo-Neptune HAT-P-11b
• Transit confirmation and improved stellar and planet parameters for the super-Earth HD 97658 b and its host star
• GJ 1214b revised. Improved trigonometric parallax, stellar parameters, orbital solution, and bulk properties for the super-Earth GJ 1214b
• Aggregate Hazes in Exoplanet Atmospheres
• 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
• The Oblique Orbit of WASP-107b from K2 Photometry
• Connecting planet formation and astrochemistry: Refractory carbon depletion leading to super-stellar C/O in giant planetary atmospheres
• Sulfur-driven Haze Formation in Warm CO2-rich Exoplanet Atmospheres
• Deciphering the atmosphere of HAT-P-12b: solving discrepant results
• ARES V: No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b
• Microphysical Modeling of Mineral Clouds in GJ1214 b and GJ436 b: Predicting Upper Limits on the Cloud-Top Height
• HAT-P-38b: A Saturn-Mass Planet Transiting a Late G Star
• Modeling the effects of inhomogeneous aerosols on the hot Jupiter Kepler-7b's atmospheric circulation
• Photochemical hazes in sub-Neptunian atmospheres with focus on GJ 1214 b
• Chemistry of Temperate Super-Earth and Mini-Neptune Atmospheric Hazes from Laboratory Experiments
• High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood
• Detectable molecular features above hydrocarbon haze via transmission spectroscopy with JWST: Case studies of GJ 1214b-, GJ 436b-, HD 97658b-, and Kepler-51b-like planets
• A Hubble PanCET Study of HAT-P-11b: A Cloudy Neptune with a Low Atmospheric Metallicity
• GJ1214: Rotation period, starspots, and uncertainty on the optical slope of the transmission spectrum
• Clouds of Fluffy Aggregates: How They Form in Exoplanetary Atmospheres and Influence Transmission Spectra
• Haze Evolution in Temperate Exoplanet Atmospheres Through Surface Energy Measurements
• Starspots on WASP-107 and pulsations of WASP-118
• Impact of photochemical hazes and gases on exoplanet atmospheric thermal structure
• Transmission spectroscopy for the warm sub-Neptune HD3167c: evidence for molecular absorption and a possible high metallicity atmosphere
• TOI-674b: an oasis in the desert of exo-Neptunes transiting a nearby M dwarf
• The First Near-Infrared Transmission Spectrum of HIP 41378 f, a Low-Mass Temperate Jovian World in a Multi-Planet System
• Closed-formed ab initio solutions of geometric albedos and reflected light phase curves of exoplanets
• A Featureless Infrared Transmission Spectrum for the Super-Puff Planet Kepler-79d
• Precise masses for the transiting planetary system HD 106315 with HARPS
• Discovery of the secondary eclipse of HAT-P-11 b
• The role of clouds on the depletion of methane and water dominance in the transmission spectra of irradiated exoplanets
• A Search for Additional Bodies in the GJ 1132 Planetary System from 21 Ground-based Transits and a 100 Hour Spitzer Campaign
• An extremely low-density and temperate giant exoplanet
• Indications for transit timing variations in the exo-Neptune HAT-P-26b
• On the radial velocity detection of additional planets in transiting, slowly rotating M-dwarf systems: the case of GJ 1132
• Theoretical Transmission Spectra of Exoplanet Atmospheres with Hydrocarbon Haze. II. Dependence on UV Irradiation Intensity, Metallicity, C/O Ratio, Eddy Diffusion Coefficient, and Temperature
• Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs

Cited by in corpus (13)

• Clouds and Clarity: Revisiting Atmospheric Feature Trends in Neptune-size Exoplanets
• Exoplanet Volatile Carbon Content as a Natural Pathway for Haze Formation
• A Temperature Trend for Clouds and Hazes in Exoplanets Atmospheres
• Importance of Sample Selection in Exoplanet Atmosphere Population Studies
• TOI-3785 b: A Low-Density Neptune Orbiting an M2-Dwarf Star
• The unusual M-dwarf Warm Jupiter TOI-1899~b: Refinement of orbital and planetary parameters
• The Similar Seven: A set of very-alike exoplanets to test correlations between system parameters and atmospheric properties
• Experimental Investigation of the Photochemical Production of Hydrocarbons in Warm Gas Giant Exoplanet Atmospheres
• Three-dimensional Transport-induced Chemistry on Temperate sub-Neptune K2-18b, Part I: the Effects of Atmospheric Dynamics
• Diversity of Exoplanets
• Ground-Based Reconnaissance Observations of 21 Exoplanet Atmospheres with the Exoplanet Transmission Spectroscopy Imager
• Three-dimensional transport-induced chemistry on temperate sub-Neptune K2-18b, Part II: the combined effects of atmospheric dynamics and chemical reactions
• Impact of Clouds on the Atmosphere-Mantle Interface of Sub-Neptunes