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Physically-motivated basis functions for temperature maps of exoplanets
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Morris, Brett M., Heng, Kevin, Jones, Kathryn, Piaulet, Caroline, Demory, Brice-Olivier, Kitzmann, Daniel and Jens Hoeijmakers, H. (2022) Physically-motivated basis functions for temperature maps of exoplanets. Astronomy & Astrophysics, 660 . A123. doi:10.1051/0004-6361/202142135 ISSN 0004-6361.
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Official URL: http://dx.doi.org/10.1051/0004-6361/202142135
Abstract
Thermal phase curves of exoplanet atmospheres have revealed temperature maps as a function of planetary longitude, often by sinusoidal decomposition of the phase curve. We construct a framework for describing two-dimensional temperature maps of exoplanets with mathematical basis functions derived for a fluid layer on a rotating, heated sphere with drag/friction, which are generalisations of spherical harmonics. These basis functions naturally produce physically-motivated temperature maps for exoplanets with few free parameters. We investigate best practices for applying this framework to temperature maps of hot Jupiters by splitting the problem into two parts: (1) we constrain the temperature map as a function of latitude by tuning the basis functions to reproduce general circulation model outputs, since disk-integrated phase curve observations do not constrain this dimension; and (2) we infer the temperature maps of real hot Jupiters using original reductions of several Spitzer phase curves, which directly constrain the temperature variations with longitude. The resulting phase curves can be described with only three free parameters per bandpass – an efficiency improvement over the usual five or so used to describe sinusoidal decompositions of phase curves. Upon obtaining the hemispherically averaged day side and night side temperatures, the standard approach would be to use zero-dimensional box models to infer the Bond albedo and redistribution efficiency. We elucidate the limitation of these box models by demonstrating that negative Bond albedos may be obtained due to a choice of boundary condition on the night side temperature. We propose generalized definitions for the Bond albedo and heat redistribution efficiency for use with two-dimensional (2D) temperature maps. Open-source software called kelp is provided to efficiently compute the 2D temperature maps, phase curves, albedos and redistribution efficiencies.
Item Type: | Journal Article | ||||||||||||||||||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||||||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||||||||||||||
Library of Congress Subject Headings (LCSH): | Extrasolar planets, Planetary systems, Planets -- Atmospheres, Satellites -- Atmospheres, Astronomical photometry | ||||||||||||||||||||||||
Journal or Publication Title: | Astronomy & Astrophysics | ||||||||||||||||||||||||
Publisher: | EDP Sciences | ||||||||||||||||||||||||
ISSN: | 0004-6361 | ||||||||||||||||||||||||
Official Date: | 29 April 2022 | ||||||||||||||||||||||||
Dates: |
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Volume: | 660 | ||||||||||||||||||||||||
Article Number: | A123 | ||||||||||||||||||||||||
DOI: | 10.1051/0004-6361/202142135 | ||||||||||||||||||||||||
Status: | Peer Reviewed | ||||||||||||||||||||||||
Publication Status: | Published | ||||||||||||||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||||||||||||||
Date of first compliant deposit: | 15 June 2022 | ||||||||||||||||||||||||
Date of first compliant Open Access: | 15 June 2022 | ||||||||||||||||||||||||
RIOXX Funder/Project Grant: |
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