Self-luminous and Irradiated Exoplanetary Atmospheres Explored with HELIOS

We present new methodological features and physical ingredients included in the one-dimensional radiative transfer code HELIOS, improving the hemispheric two-stream formalism. We conduct a thorough intercomparison survey with several established forward models, including COOLTLUSTY and PHOENIX, and...

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Bibliographic Details
Published in:The Astronomical journal 2019-05, Vol.157 (5), p.170
Main Authors: Malik, Matej, Kitzmann, Daniel, Mendonça, João M., Grimm, Simon L., Marleau, Gabriel-Dominique, Linder, Esther F., Tsai, Shang-Min, Heng, Kevin
Format: Article
Language:English
Subjects:
ABSORPTION
Alkali metals
AMBIENT TEMPERATURE
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Atmosphere
Atmospheric models
ATOMS
CALCULATION METHODS
CORRECTIONS
Effective temperatures
EMISSION
EMISSION SPECTRA
Extrasolar planets
FORECASTING
GRAVITATION
HYDRIDES
HYDROGEN
Hydrogen storage
Metal oxides
METALLICITY
methods: numerical
OPACITY
Organic chemistry
OXIDES
PLANETARY ATMOSPHERES
Planetary evolution
PLANETS
planets and satellites: atmospheres
RADIANT HEAT TRANSFER
Radiation
Radiation absorption
Radiative transfer
SATELLITE ATMOSPHERES
SCATTERING
Short wave radiation
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Summary:We present new methodological features and physical ingredients included in the one-dimensional radiative transfer code HELIOS, improving the hemispheric two-stream formalism. We conduct a thorough intercomparison survey with several established forward models, including COOLTLUSTY and PHOENIX, and find satisfactory consistency with their results. Then, we explore the impact of (i) different groups of opacity sources, (ii) a stellar path length adjustment, and (iii) a scattering correction on self-consistently calculated atmospheric temperatures and planetary emission spectra. First, we observe that temperature-pressure (T-P) profiles are very sensitive to the opacities included, with metal oxides, hydrides, and alkali atoms (and ionized hydrogen) playing an important role in the absorption of shortwave radiation (in very hot surroundings). Moreover, if these species are sufficiently abundant, they are likely to induce nonmonotonic T-P profiles. Second, without the stellar path length adjustment, the incoming stellar flux is significantly underestimated for zenith angles above 80°, which somewhat affects the upper atmospheric temperatures and the planetary emission. Third, the scattering correction improves the accuracy of the computation of the reflected stellar light by ∼10%. We use HELIOS to calculate a grid of cloud-free atmospheres in radiative-convective equilibrium for self-luminous planets for a range of effective temperatures, surface gravities, metallicities, and C/O ratios to be used by planetary evolution studies. Furthermore, we calculate dayside temperatures and secondary eclipse spectra for a sample of exoplanets for varying chemistry and heat redistribution. These results may be used to make predictions on the feasibility of atmospheric characterizations with future observations.
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/1538-3881/ab1084