Jens Hoeijmakers
ASSOCIATE SENIOR LECTURER
Physically-motivated basis functions for temperature maps of exoplanets
Author
Summary, in English
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.
Department/s
- Lund Observatory - Has been reorganised
- Astrophysics
Publishing year
2022-04
Language
English
Publication/Series
Astronomy and Astrophysics
Volume
660
Document type
Journal article
Publisher
EDP Sciences
Topic
- Astronomy, Astrophysics and Cosmology
Keywords
- Methods: analytical
- Methods: observational
- Planets and satellites: atmospheres
- Planets and satellites: gaseous planets
- Radio continuum: planetary systems
- Techniques: photometric
Status
Published
ISBN/ISSN/Other
- ISSN: 0004-6361