A transition between the hot and the ultra-hot Jupiter atmospheres

Abstract

[Abridged] A key hypothesis in the field of exoplanet atmospheres is the trend of atmospheric thermal structure with planetary equilibrium temperature. We explore this trend and report here the first statistical detection of a transition in the near-infrared (NIR) atmospheric emission between hot and ultra-hot Jupiters. We measure this transition using secondary eclipse observations and interpret this phenomenon as changes in atmospheric properties, and more specifically in terms of transition from non-inverted to inverted thermal profiles. We examine a sample of 78 hot Jupiters with secondary eclipse measurements at 3.6 μm and 4.5 μm measured with Spitzer Infrared Array Camera (IRAC). We measure the deviation of the data from the blackbody, which we define as the difference between the observed 4.5 μm eclipse depth and that expected at this wavelength based on the brightness temperature measured at 3.6 μm. We study how the deviation between 3.6 and 4.5 μm changes with theoretical predictions with equilibrium temperature and incoming stellar irradiation. We reveal a clear transition in the observed emission spectra of the hot Jupiter population at 1660 +/- 100 K in the zero albedo, full redistribution equilibrium temperature. We find the hotter exoplanets have even hotter daysides at 4.5 μm compared to 3.6 μm, which manifests as an exponential increase in the emitted power of the planets with stellar insolation. We propose that the measured transition is a result of seeing carbon monoxide in emission due to the formation of temperature inversions in the atmospheres of the hottest planets. These thermal inversions could be caused by the presence of atomic and molecular species with high opacities in the optical and/or the lack of cooling species. We find that the population of hot Jupiters statistically disfavors high C/O planets (C/O>= 0.85).

Accepted 11th May 2020

References in corpus (32)

• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• Detection of Thermal Emission from an Extrasolar Planet
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
• The Broadband Infrared Emission Spectrum of the Exoplanet HD 189733b
• Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-Level Decorrelation
• Theoretical Spectral Models of the Planet HD 209458b with a Thermal Inversion and Water Emission Bands
• An ultrahot gas-giant exoplanet with a stratosphere
• A giant planet undergoing extreme ultraviolet irradiation by its hot massive-star host
• The Exoplanet Orbit Database II: Updates to exoplanets.org
• A Universal Scaling for the Energetics of Relativistic Jets From Black Hole Systems
• A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b
• Methane, Carbon Monoxide, and Ammonia in Brown Dwarfs and Self-Luminous Giant Planets
• Hot Nights on Extrasolar Planets: Mid-IR Phase Variations of Hot Jupiters
• New Analysis Indicates No Thermal Inversion in the Atmosphere of HD 209458b
• Balancing the Energy Budget of Short-Period Giant Planets: Evidence for Reflective Clouds and Optical Absorbers
• On the Absorption and Redistribution of Energy in Irradiated Planets
• Neutral Iron Emission Lines From The Day-side Of KELT-9b -- The GAPS Programme With HARPS-N At TNG XX
• Treatment of overlapping gaseous absorption with the correlated-k method in hot Jupiter and brown dwarf atmosphere models
• Atmospheric Characterization of the Hot Jupiter Kepler-13Ab
• 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
• Thermal Emission of Exoplanet XO-1b
• WASP-80b has a dayside within the T-dwarf range
• New Avenues for Thermal Inversions in hot Jupiters
• Evidence for H${}_2$ Dissociation and Recombination Heat Transport in the Atmosphere of KELT-9b
• The Very Low Albedo of WASP-12b From Spectral Eclipse Observations with $\text{Hubble}$
• Phase Offsets and the Energy Budgets of Hot Jupiters
• Characterization of the atmosphere of the hot Jupiter HAT-P-32Ab and the M-dwarf companion HAT-P-32B
• Hubble PanCET: An isothermal day-side atmosphere for the bloated gas-giant HAT-P-32Ab
• Colour-magnitude diagrams of transiting Exoplanets - II. A larger sample from photometric distances
• Colour-colour and colour-magnitude diagrams for Hot Jupiters

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