HELIOS: AN OPEN-SOURCE, GPU-ACCELERATED RADIATIVE TRANSFER CODE for SELF-CONSISTENT EXOPLANETARY ATMOSPHERES

Matej Malik, Luc Grosheintz, João M. Mendonça, Simon L. Grimm, Baptiste Lavie, Daniel Kitzmann, Shang Min Tsai, Adam S. Burrows, Laura Kreidberg, Megan Bedell, Jacob L. Bean, Kevin B. Stevenson, Kevin Heng

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

We present the open-source radiative transfer code named HELIOS, which is constructed for studying exoplanetary atmospheres. In its initial version, the model atmospheres of HELIOS are one-dimensional and plane-parallel, and the equation of radiative transfer is solved in the two-stream approximation with nonisotropic scattering. A small set of the main infrared absorbers is employed, computed with the opacity calculator HELIOS-K and combined using a correlated-k approximation. The molecular abundances originate from validated analytical formulae for equilibrium chemistry. We compare HELIOS with the work of Miller-Ricci & Fortney using a model of GJ 1214b, and perform several tests, where we find: model atmospheres with single-temperature layers struggle to converge to radiative equilibrium; k-distribution tables constructed with cm-1 resolution in the opacity function ( points per wavenumber bin) may result in errors %-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 "null-hypothesis" models (chemical equilibrium, radiative equilibrium, and solar elemental abundances) for six hot Jupiters. We find that the dayside emission spectra of HD 189733b and WASP-43b are consistent with the null hypothesis, while the latter consistently underpredicts the observed fluxes of WASP-8b, WASP-12b, WASP-14b, and WASP-33b. 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 carbon-to-oxygen ratios. The code is publicly available as part of the Exoclimes Simulation Platform (exoclime.net).

Original languageEnglish (US)
Article number56
JournalAstronomical Journal
Volume153
Issue number2
DOIs
StatePublished - Feb 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • methods: numerical
  • planets and satellites: atmospheres
  • radiative transfer

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