The mineral clouds on HD 209458b and HD 189733b

Helling, Christiane; Lee, Elspeth K. H.; Dobbs-Dixon, Ian; Mayne, Nathan J.; Amundsen, David Skålid; Khaimova, J.; Unger, Anders; Manners, James; Acreman, David M.; Smith, Chris

doi:10.1093/mnras/stw662

Cited by 123 publications

(112 citation statements)

References 87 publications

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“…We chose a hierarchical approach of modelling environments where we utilise 97 1D profiles extracted from the 3D GCM calculated for the cloud-free HAT-P-7b (Mansfield et al 2018) and apply our kinetic cloud formation model consistently linked to an chemical equilibrium code. Our study is the continuation of previous investigations of cloud formation in the giant gas planets HD 189733b and HD 209458b (Lee et al 2015a;Helling et al 2016;Lee et al 2016;Lines et al 2018b), and the super-hot gas giant WASP-18b in order to enable a comparative overview for these two classes of giant gas planets given that observations mainly provide snapshots of certain aspects (e.g. presence of certain gas species, existence of clouds, a hot spot off-set) of each of these planets so far.…”

Section: Introductionsupporting

confidence: 84%

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b

Helling

Iro

Corrales

et al. 2019

A&A

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Context. Of the presently known ≈ 3900 exoplanets, sparse spectral observations are available for ≈ 100. Ultra-hot Jupiters have recently attracted interest from observers and theoreticians alike, as they provide observationally accessible test cases. Aims. We aim to study cloud formation on the ultra-hot Jupiter HAT-P-7b, the resulting composition of the local gas phase, and how their global changes affect wavelength-dependent observations utilised to derive fundamental properties of the planet. Methods. We apply a hierarchical modelling approach as a virtual laboratory to study cloud formation and gas-phase chemistry. We utilise 97 vertical 1D profiles of a 3D GCM for HAT-P-7b to evaluate our kinetic cloud formation model consistently with the local equilibrium gas-phase composition. We use maps and slice views to provide a global understanding of the cloud and gas chemistry. Results. The day/night temperature difference on HAT-P-7b (∆T ≈ 2500 K) causes clouds to form on the nightside (dominated by H 2 /He) while the dayside (dominated by H/He) retains cloud-free equatorial regions. The cloud particles vary in composition and size throughout the vertical extension of the cloud, but also globally. TiO 2 [s]/Al 2 O 3 [s]/CaTiO 3 [s]-particles of cm-sized radii occur in the higher dayside-latitudes, resulting in a dayside dominated by gas-phase opacity. The opacity on the nightside, however, is dominated by 0.01 . . . 0.1 µm particles made of a material mix dominated by silicates. The gas pressure at which the atmosphere becomes optically thick is ∼ 10 −4 bar in cloudy regions, and ∼ 0.1 bar in cloud-free regions. Conclusions. HAT-P-7b features strong morning/evening terminator asymmetries, providing an example of patchy clouds and azimuthally-inhomogeneous chemistry. Variable terminator properties may be accessible by ingress/egress transmission photometry (e.g., CHEOPS and PLATO) or spectroscopy. The large temperature differences of ≈2500 K result in an increasing geometrical extension from the night-to the dayside. The chemcial equilibrium H 2 O abundance at the terminator changes by < 1 dex with altitude and 0.3 dex (a factor of 2) across the terminator for a given pressure, indicating that H 2 O abundances derived from transmission spectra can be representative of the well-mixed metallicity at P 10 bar. We suggest the atmospheric C/O as an important tool to trace the presence and location of clouds in exoplanet atmospheres. The atmospheric C/O can be sub-and supersolar due to cloud formation. Phase curve variability of HAT-P-7b is unlikely to be caused by dayside clouds.

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Section: Introductionsupporting

confidence: 84%

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b

Helling

Iro

Corrales

et al. 2019

A&A

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“…Our results have shown that the super-rotating equatorial jet, found as a solution for hot Jupiter atmospheres from several models (see for example Cooper & Showman 2005;Menou & Rauscher 2009;Rauscher & Menou 2010;Heng et al 2011;Dobbs-Dixon & Agol 2013;Parmentier et al 2013;Showman et al 2015;Helling et al 2016;Kataria et al 2016;Lee et al 2016), is robust in our setup. Our model does not include a drag or friction at the bottom boundary potentially responsible for removing some of the dependence on initial conditions (see Liu & Showman 2013;Cho et al 2015).…”

Section: Resultssupporting

confidence: 59%

Results from a set of three-dimensional numerical experiments of a hot Jupiter atmosphere

Mayne

Debras

Baraffe

et al. 2017

A&A

112

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We present highlights from a large set of simulations of a hot Jupiter atmosphere, nominally based on HD 209458b, aimed at exploring both the evolution of the deep atmosphere, and the acceleration of the zonal flow or jet. We find the occurrence of a super-rotating equatorial jet is robust to changes in various parameters, and over long timescales, even in the absence of strong inner or bottom boundary drag. This jet is diminished in one simulation only, where we strongly force the deep atmosphere equator-to-pole temperature gradient over long timescales. Finally, although the eddy momentum fluxes in our atmosphere show similarities with the proposed mechanism for accelerating jets on tidally-locked planets, the picture appears more complex. We present tentative evidence for a jet driven by a combination of eddy momentum transport and mean flow.

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“…However, Fe[s] rich grains are expected to reside below the photosphere of HD 189733b (Lee et al 2015;Helling et al 2016a), where they would have negligible effects on the observable scattered and emitted light.…”

Section: Discussionmentioning

confidence: 99%

“…This is converted into a mass opacity by the relation κ sca,H 2 (λ) = n H 2 σ sca,H 2 (λ)/ρ gas . The abundance of molecular H 2 (n H 2 [cm −3 ]) is calculated at each cell assuming chemical equilibrium using the routines from Helling et al (2016a).…”

Section: Cloud and Gas Opacitymentioning

confidence: 99%

Dynamic mineral clouds on HD 189733b

Lee

Wood

Dobbs-Dixon

et al. 2017

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Context. As the 3D spatial properties of exoplanet atmospheres are being observed in increasing detail by current and new generations of telescopes, the modelling of the 3D scattering effects of cloud forming atmospheres with inhomogeneous opacity structures becomes increasingly important to interpret observational data. Aims. We model the scattering and emission properties of a simulated cloud forming, inhomogeneous opacity, hot Jupiter atmosphere of HD 189733b. We compare our results to available Hubble Space Telescope (HST) and Spitzer data and quantify the effects of 3D multiple scattering on observable properties of the atmosphere. We discuss potential observational properties of HD 189733b for the upcoming Transiting Exoplanet Survey Satellite (TESS) and CHaracterising ExOPlanet Satellite (CHEOPS) missions. Methods. We developed a Monte Carlo radiative transfer code and applied it to post-process output of our 3D radiative-hydrodynamic, cloud formation simulation of HD 189733b. We employed three variance reduction techniques, i.e. next event estimation, survival biasing, and composite emission biasing, to improve signal to noise of the output. For cloud particle scattering events, we constructed a log-normal area distribution from the 3D cloud formation radiative-hydrodynamic results, which is stochastically sampled in order to model the Rayleigh and Mie scattering behaviour of a mixture of grain sizes. Results. Stellar photon packets incident on the eastern dayside hemisphere show predominantly Rayleigh, single-scattering behaviour, while multiple scattering occurs on the western hemisphere. Combined scattered and thermal emitted light predictions are consistent with published HST and Spitzer secondary transit observations. Our model predictions are also consistent with geometric albedo constraints from optical wavelength ground-based polarimetry and HST B band measurements. We predict an apparent geometric albedo for HD 189733b of 0.205 and 0.229, in the TESS and CHEOPS photometric bands respectively. Conclusions. Modelling the 3D geometric scattering effects of clouds on observables of exoplanet atmospheres provides an important contribution to the attempt to determine the cloud properties of these objects. Comparisons between TESS and CHEOPS photometry may provide qualitative information on the cloud properties of nearby hot Jupiter exoplanets.

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The mineral clouds on HD 209458b and HD 189733b

Cited by 123 publications

References 87 publications

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b

Results from a set of three-dimensional numerical experiments of a hot Jupiter atmosphere

Dynamic mineral clouds on HD 189733b

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