Volume 594, October 2016
|Number of page(s)
|Planets and planetary systems
|13 October 2016
The effects of consistent chemical kinetics calculations on the pressure-temperature profiles and emission spectra of hot Jupiters
1 Astrophysics Group, University of Exeter, EX4 4QL Exeter, UK
2 Maison de la Simulation, CEA-CNRS-INRIA-UPS-UVSQ, USR 3441 Centre d’étude de Saclay, 91191 Gif-Sur-Yvette, France
3 Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10025, USA
4 NASA Goddard Institute for Space Studies, New York, NY 10025, USA
5 Univ. Lyon, ENS de Lyon, Univ. Lyon1, CNRS, CRAL, UMR 5574, 69007 Lyon, France
6 Intituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
Received: 26 April 2016
Accepted: 13 July 2016
In this work we investigate the impact of calculating non-equilibrium chemical abundances consistently with the temperature structure for the atmospheres of highly-irradiated, close-in gas giant exoplanets. Chemical kinetics models have been widely used in the literature to investigate the chemical compositions of hot Jupiter atmospheres which are expected to be driven away from chemical equilibrium via processes such as vertical mixing and photochemistry. All of these models have so far used pressure–temperature (P–T) profiles as fixed model input. This results in a decoupling of the chemistry from the radiative and thermal properties of the atmosphere, despite the fact that in nature they are intricately linked. We use a one-dimensional radiative-convective equilibrium model, ATMO, which includes a sophisticated chemistry scheme to calculate P–T profiles which are fully consistent with non-equilibrium chemical abundances, including vertical mixing and photochemistry. Our primary conclusion is that, in cases of strong chemical disequilibrium, consistent calculations can lead to differences in the P–T profile of up to 100 K compared to the P–T profile derived assuming chemical equilibrium. This temperature change can, in turn, have important consequences for the chemical abundances themselves as well as for the simulated emission spectra. In particular, we find that performing the chemical kinetics calculation consistently can reduce the overall impact of non-equilibrium chemistry on the observable emission spectrum of hot Jupiters. Simulated observations derived from non-consistent models could thus yield the wrong interpretation. We show that this behaviour is due to the non-consistent models violating the energy budget balance of the atmosphere.
Key words: planets and satellites: atmospheres / planets and satellites: composition
© ESO, 2016
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