A dayside thermal inversion in the atmosphere of WASP-19b

Abstract

Observations of ultra-hot Jupiters indicate the existence of thermal inversion in their atmospheres with day-side temperatures greater than 2200 K. Various physical mechanisms such as non-local thermal equilibrium, cloud formation, disequilibrium chemistry, ionisation, hydrodynamic waves and associated energy, have been omitted in previous spectral retrievals while they play an important role on the thermal structure of their upper atmospheres.We aim at exploring the atmospheric properties of WASP-19b to understand its largely featureless thermal spectra using a state-of-the-art atmosphere code that includes a detailed treatment of the most important physical and chemical processes at play in such atmospheres.We used the one-dimensional line-by-line radiative transfer code PHOENIX in its spherical symmetry configuration including the BT-Settl cloud model and C/O disequilibrium chemistry to analyse the observed thermal spectrum of WASP-19b. Results. We find evidence for a thermal inversion in the day-side atmosphere of the highly irradiated ultra-hot Jupiter WASP-19b with Teq ~ 2700 K. At these high temperatures we find that H2O dissociates thermally at pressure below 10^-2 bar. The inverted temperature-pressure profiles of WASP-19b show the evidence of CO emission features at 4.5 micron in its secondary eclipse spectra.We find that the atmosphere ofWASP-19b is thermally inverted.We infer that the thermal inversion is due to the strong impinging radiation. We show that H2O is partially dissociated in the upper atmosphere above about tau = 10^-2, but is still a significant contributor to the infrared-opacity, dominated by CO. The high-temperature and low-density conditions cause H2O to have a flatter opacity profile than in non-irradiated brown dwarfs.Altogether these factors makes H2O more difficult to identify in WASP-19b.

3 figures, accepted for publication in A&A

References in corpus (14)

• Can TiO Explain Thermal Inversions in the Upper Atmospheres of Irradiated Giant Planets?
• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• An ultrahot gas-giant exoplanet with a stratosphere
• Detection of titanium oxide in the atmosphere of a hot Jupiter
• High-Resolution Spectroscopic Detection of TiO and Stratosphere in the Day-side of WASP-33b
• New Analysis Indicates No Thermal Inversion in the Atmosphere of HD 209458b
• TiO and VO broad band absorption features in the optical spectrum of the atmosphere of the hot-Jupiter HD209458b
• K-H_2 Quasi-molecular absorption detected in the T-dwarf epsilon Indi Ba
• A method for the direct determination of the surface gravities of transiting extrasolar planets
• Deciphering the Atmospheric Composition of WASP-12b: A Comprehensive Analysis of its Dayside Emission
• Evidence for a Dayside Thermal Inversion and High Metallicity for the Hot Jupiter WASP-18b
• A photometric study of the hot exoplanet WASP-19b
• Forecasting the Impact of Stellar Activity on Transiting Exoplanet Spectra
• z'-band Ground-Based Detection of the Secondary Eclipse of WASP-19b

Cited by in corpus (3)

• The Effect of Metallicity on the Non-Equilibrium Abundance of Hydrogen Dominated Exoplanet Atmosphere
• A Global Perspective with Updated Constraints on the Ultra-hot Jupiter WASP-19b: Atmospheric Properties and Stellar Activity
• A new method to correct for host star variability in multi-epoch observations of exoplanet transmission spectra