A library of self-consistent simulated exoplanet atmospheres

Abstract

We present a publicly available library of model atmospheres with radiative-convective equilibrium Pressure-Temperature (P-T) profiles fully consistent with equilibrium chemical abundances, and the corresponding emission and transmission spectrum with R∼5000 at 0.2 µm decreasing to R∼35 at 30 µm, for 89 hot Jupiter exoplanets, for four re-circulation factors, six metallicities and six C/O ratios. We find the choice of condensation process (local/rainout) alters the P-T profile and thereby the spectrum substantially, potentially detectable by JWST. We find H− opacity can contribute to form a strong temperature inversion in ultra-hot Jupiters for C/O ratios ≥ 1 and can make transmission spectra features flat in the optical, alongside altering the entire emission spectra. We highlight how adopting different model choices such as thermal ionisation, opacities, line-wing profiles and the methodology of varying the C/O ratio, effects the P-T structure and the spectrum. We show the role of Fe opacity to form primary/secondary inversion in the atmosphere. We use WASP-17b and WASP-121b as test cases to demonstrate the effect of grid parameters across their full range, while highlighting some important findings, concerning the overall atmospheric structure, chemical transition regimes and their observables. Finally, we apply this library to the current transmission and emission spectra observations of WASP-121b, which shows H2O and tentative evidence for VO at the limb, and H2O emission feature indicative of inversion on the dayside, with very low energy redistribution, thereby demonstrating the applicability of library for planning and interpreting observations of transmission and emission spectrum.

HST PanCET Program: A Complete Near-UV to Infrared Transmission Spectrum for the Hot Jupiter WASP-79b

“…Our retrieved terminator temperature for WASP-79b (∼1000 K) lies in a regime where H − opacity would not be expected under equilibrium considerations. In comparison, the self-consistent models of Goyal et al (2020) predict 1 mbar temperatures of ∼2000 K for WASP-79b (assuming C/O = 0.5, M/H = 10× solar, and recirculation factor of unity). However, our three retrieval analyses assumed a uniform (1D) composition and temperature across the terminator.…”

“…H 2 dissociation is generally expected to occur on the day sides of "ultra-hot" Jupiters (e.g., Bell & Cowan 2018), with prominent H − opacity expected around 2500 K (Arcangeli et al 2018). Under the assumption of chemical equilibrium, H − abundances decrease for lower temperatures, with observable signatures in transmission spectra not expected below ∼2100 K (Goyal et al 2020).…”

Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone

“…To explore the ability of JWST to constrain WASP-62ʼs C/O ratio, we additionally injected CO, CO 2 , and CH 4 abundances into our model. The representative values were taken to be the 10 mbar abundances of these species from the self-consistent model grid of Goyal et al (2020), assumed uniform throughout the atmosphere. We then simulated JWST ERS observations with PandExo 22 (Batalha et al 2017)-in the Panchromatic Transmission configuration outlined by Bean et al (2018)-spanning four transits across the following modes:…”

“…Equilibrium chemistry expectations for silicates suggest that the dominant Si-bearing species are SiO and SiS at ∼1400 K (Visscher et al 2010;Woitke et al 2018). We investigate predictions for Si-bearing species in the atmosphere of WASP-62b using the planet-specific forward model ATMO grid (e.g., Tremblin et al 2015;Goyal et al 2020) of 1D radiative-convective equilibrium pressure-temperature profiles with corresponding self-consistent equilibrium chemistry. This grid of model atmospheres spans a range of recirculation factors (RCF), metallicities, and C/O ratios.…”

“…We produced a range of C/O ratios by varying the oxygen abundance O/H, as detailed in Sections 4 and 2.3 of the supplementary material ofGoyal et al (2020).…”