HELIOS: An Opensource, GPUaccelerated Radiative Transfer Code for Selfconsistent Exoplanetary Atmospheres
Abstract
We present the opensource radiative transfer code named HELIOS, which is constructed for studying exoplanetary atmospheres. In its initial version, the model atmospheres of HELIOS are onedimensional and planeparallel, and the equation of radiative transfer is solved in the twostream approximation with nonisotropic scattering. A small set of the main infrared absorbers is employed, computed with the opacity calculator HELIOSK and combined using a correlatedk approximation. The molecular abundances originate from validated analytical formulae for equilibrium chemistry. We compare HELIOS with the work of MillerRicci & Fortney using a model of GJ 1214b, and perform several tests, where we find: model atmospheres with singletemperature layers struggle to converge to radiative equilibrium; kdistribution tables constructed with ≳ 0.01 cm^{1} resolution in the opacity function (≲ {10}^{3} points per wavenumber bin) may result in errors ≳ 1%10% in the synthetic spectra; and a diffusivity factor of 2 approximates well the exact radiative transfer solution in the limit of pure absorption. We construct “nullhypothesis” models (chemical equilibrium, radiative equilibrium, and solar elemental abundances) for six hot Jupiters. We find that the dayside emission spectra of HD 189733b and WASP43b are consistent with the null hypothesis, while the latter consistently underpredicts the observed fluxes of WASP8b, WASP12b, WASP14b, and WASP33b. We demonstrate that our results are somewhat insensitive to the choice of stellar models (blackbody, Kurucz, or PHOENIX) and metallicity, but are strongly affected by higher carbontooxygen ratios. The code is publicly available as part of the Exoclimes Simulation Platform (exoclime.net).
 Publication:

The Astronomical Journal
 Pub Date:
 February 2017
 DOI:
 10.3847/15383881/153/2/56
 arXiv:
 arXiv:1606.05474
 Bibcode:
 2017AJ....153...56M
 Keywords:

 methods: numerical;
 planets and satellites: atmospheres;
 radiative transfer;
 Astrophysics  Earth and Planetary Astrophysics;
 Physics  Atmospheric and Oceanic Physics
 EPrint:
 24 pages, 14 figures, accepted for publication in ApJ