A library of ATMO forward model transmission spectra for hot Jupiter exoplanets

Abstract

We present a grid of forward model transmission spectra, adopting an\nisothermal temperature-pressure profile, alongside corresponding equilibrium\nchemical abundances for 117 observationally significant hot exoplanets\n(Equilibrium Temperatures of 547-2710 K). This model grid has been developed\nusing a 1D radiative-convective-chemical equilibrium model termed ATMO, with\nup-to-date high temperature opacities. We present an interpretation of\nobservations of ten exoplanets, including best fit parameters and $\\chi^{2}$\nmaps. In agreement with previous works, we find a continuum from clear to\nhazy/cloudy atmospheres for this sample of hot Jupiters. The data for all the\n10 planets are consistent with sub-solar to solar C/O ratio, 0.005 to 10 times\nsolar metallicity and water rather than a methane dominated infrared spectra.\nWe then explore the range of simulated atmospheric spectra for different\nexoplanets, based on characteristics such as temperature, metallicity,\nC/O-ratio, haziness and cloudiness. We find a transition value for the\nmetallicity between 10 and 50 times solar, which leads to substantial changes\nin the transmission spectra. We also find a transition value of C/O ratio, from\nwater to carbon species dominated infrared spectra, as found by previous works,\nrevealing a temperature dependence of this transition point ranging from\n$\\sim$0.56 to $\\sim$1-1.3 for equilibrium temperatures from $\\sim$900 to\n$\\sim$2600 K. We highlight the potential of the spectral features of HCN and\nC$_2$H$_2$ to constrain the metallicities and C/O ratios of planets, using JWST\nobservations. Finally, our entire grid ($\\sim$460,000 simulations) is publicly\navailable and can be used directly with the JWST simulator PandExo for planning\nobservations.\n