Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b II. Mapping the effects of gas kinetics. (arXiv:2001.03668v1 [astro-ph.EP])

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b II. Mapping the effects of gas kinetics. (arXiv:2001.03668v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Molaverdikhani_K/0/1/0/all/0/1">Karan Molaverdikhani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Helling_C/0/1/0/all/0/1">Christiane Helling</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lew_B/0/1/0/all/0/1">Ben W.P. Lew</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+MacDonald_R/0/1/0/all/0/1">Ryan J. MacDonald</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Samra_D/0/1/0/all/0/1">Dominic Samra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Iro_N/0/1/0/all/0/1">Nicolas Iro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Woitke_P/0/1/0/all/0/1">Peter Woitke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Parmentier_V/0/1/0/all/0/1">Vivien Parmentier</a>

The atmospheres of ultra-hot Jupiters are commonly considered to be at
thermochemical equilibrium. We aim to provide disequilibrium chemistry maps for
a global understanding of the chemistry in HAT-P-7b’s atmosphere and assess the
importance of disequilibrium chemistry on UHJs.

We apply a hierarchical modelling approach utilising 97 1D atmospheric
profiles from 3D GCM of HAT-P-7b. For each 1D profile, we evaluate our kinetic
cloud formation model consistently with the local gas-phase composition in
chemical equilibrium. We then evaluate quenching results from a zeroth-order
approximation in comparison to a kinetic gas-phase approach.

We find that the zeroth-order approach of estimating quenching points agrees
well with the full gas-kinetic modeling results. Chemical disequilibrium has
the greatest effect on the nightside and morning abundance of species such as
H, H$_2$O, CH$_4$, CO$_2$, HCN, and all C$_n$H$_m$ molecules; heavier
C$_n$H$_m$ molecules are more affected by disequilibrium processes. CO
abundance, however, is affected only marginally. While dayside abundances also
notably change, those around the evening terminator of HAT-P-7b are the least
affected by disequilibrium processes. The latter finding may partially explain
the consistency of observed transmission spectra of UHJs with atmospheres in
thermochemical equilibrium. Photochemistry only negligibly affects molecular
abundances and quenching levels.

In general, the quenching points of HAT-P-7b’s atmosphere are at much lower
pressures in comparison to the cooler hot-jupiters. We propose several avenues
to look for the effect of disequilibrium processes on UHJs that are, in
general, based on abundance and opacity measurements at different local times.
It remains a challenge to completely disentangle this from the chemical effects
of clouds and that of a primordial non-solar abundance.

The atmospheres of ultra-hot Jupiters are commonly considered to be at
thermochemical equilibrium. We aim to provide disequilibrium chemistry maps for
a global understanding of the chemistry in HAT-P-7b’s atmosphere and assess the
importance of disequilibrium chemistry on UHJs.

We apply a hierarchical modelling approach utilising 97 1D atmospheric
profiles from 3D GCM of HAT-P-7b. For each 1D profile, we evaluate our kinetic
cloud formation model consistently with the local gas-phase composition in
chemical equilibrium. We then evaluate quenching results from a zeroth-order
approximation in comparison to a kinetic gas-phase approach.

We find that the zeroth-order approach of estimating quenching points agrees
well with the full gas-kinetic modeling results. Chemical disequilibrium has
the greatest effect on the nightside and morning abundance of species such as
H, H$_2$O, CH$_4$, CO$_2$, HCN, and all C$_n$H$_m$ molecules; heavier
C$_n$H$_m$ molecules are more affected by disequilibrium processes. CO
abundance, however, is affected only marginally. While dayside abundances also
notably change, those around the evening terminator of HAT-P-7b are the least
affected by disequilibrium processes. The latter finding may partially explain
the consistency of observed transmission spectra of UHJs with atmospheres in
thermochemical equilibrium. Photochemistry only negligibly affects molecular
abundances and quenching levels.

In general, the quenching points of HAT-P-7b’s atmosphere are at much lower
pressures in comparison to the cooler hot-jupiters. We propose several avenues
to look for the effect of disequilibrium processes on UHJs that are, in
general, based on abundance and opacity measurements at different local times.
It remains a challenge to completely disentangle this from the chemical effects
of clouds and that of a primordial non-solar abundance.

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