A library of ATMO forward model transmission spectra for hot Jupiter exoplanets Article - Mars 2018

Jayesh Goyal, Nathan Mayne, David Sing, Benjamin Drummond, Pascal Tremblin, David Amundsen, Thomas Evans, Aarynn Carter, Jessica Spake, Isabelle Baraffe, Nikolay Nikolov, James Manners, Gilles Chabrier, Eric Hébrard

Jayesh Goyal, Nathan Mayne, David Sing, Benjamin Drummond, Pascal Tremblin, David Amundsen, Thomas Evans, Aarynn Carter, Jessica Spake, Isabelle Baraffe, Nikolay Nikolov, James Manners, Gilles Chabrier, Eric Hébrard, « A library of ATMO forward model transmission spectra for hot Jupiter exoplanets  », Monthly Notices of the Royal Astronomical Society, mars 2018, pp. 5158 - 5185. ISSN 0035-8711

Abstract

We present a grid of forward model transmission spectra, adopting an isothermal temperature-pressure profile, alongside corresponding equilibrium chemical abundances for 117 observationally significant hot exoplanets (equilibrium temperatures of 547–2710 K). This model grid has been developed using a 1D radiative–convective–chemical equilibrium model termed ATMO, with up-to-date high-temperature opacities. We present an interpretation of observations of 10 exoplanets, including best-fitting parameters and χ2 maps. In agreement with previous works, we find a continuum from clear to hazy/cloudy atmospheres for this sample of hot Jupiters. The data for all the 10 planets are consistent with subsolar to solar C/O ratio, 0.005 to 10 times solar metallicity and water rather than methane-dominated infrared spectra. We then explore the range of simulated atmospheric spectra for different exoplanets, based on characteristics such as temperature, metallicity, C/O ratio, haziness and cloudiness. We find a transition value for the metallicity between 10 and 50 times solar, which leads to substantial changes in the transmission spectra. We also find a transition value of C/O ratio, from water to carbon species dominated infrared spectra, as found by previous works, revealing a temperature dependence of this transition point ranging from ∼0.56 to ∼1–1.3 for equilibrium temperatures from ∼900 to ∼2600 K. We highlight the potential of the spectral features of HCN and C2H2 to constrain the metallicities and C/O ratios of planets, using James Webb Space Telescope (JWST) observations. Finally, our entire grid (∼460 000 simulations) is publicly available and can be used directly with the JWST simulator PandExo for planning observations.

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