The Effect of Clouds as an Additional Opacity Source on the Inferred Metallicity of Giant Exoplanets. (arXiv:1911.01191v1 [astro-ph.EP])

The Effect of Clouds as an Additional Opacity Source on the Inferred Metallicity of Giant Exoplanets. (arXiv:1911.01191v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Poser_A/0/1/0/all/0/1">Anna Julia Poser</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nettelmann_N/0/1/0/all/0/1">Nadine Nettelmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Redmer_R/0/1/0/all/0/1">Ronald Redmer</a>

Atmospheres regulate the planetary heat loss and therefore influence
planetary thermal evolution. Uncertainty in a giant planet’s thermal state
contributes to the uncertainty in the inferred abundance of heavy elements it
contains. Within an analytic atmosphere model, we here investigate the
influence that different cloud opacities and cloud depths can have on the
metallicity of irradiated extrasolar gas giants, which is inferred from
interior models. In this work, the link between inferred metallicity and
assumed cloud properties is the thermal profile of atmosphere and interior.
Therefore, we perform coupled atmosphere, interior, and evolution calculations.
The atmosphere model includes clouds in a much simplified manner; it includes
long-wave absorption but neglects shortwave scattering. Within that model, we
show that optically thick, high clouds have negligible influence, whereas
deep-seated, optically very thick clouds can lead to warmer deep tropospheres
and therefore higher bulk heavy element mass estimates. For the young hot
Jupiter WASP-10b, we find a possible enhancement in inferred metallicity of up
to 10% due to possible silicate clouds at $sim$0.3 bar. For WASP-39b, whose
observationally derived metallicity is higher than predicted by cloudless
models, we find an enhancement by at most 50%. However, further work on cloud
properties and their self-consistent coupling to the atmospheric structure is
needed in order to reduce uncertainties in the choice of model parameter
values, in particular of cloud opacities.

Atmospheres regulate the planetary heat loss and therefore influence
planetary thermal evolution. Uncertainty in a giant planet’s thermal state
contributes to the uncertainty in the inferred abundance of heavy elements it
contains. Within an analytic atmosphere model, we here investigate the
influence that different cloud opacities and cloud depths can have on the
metallicity of irradiated extrasolar gas giants, which is inferred from
interior models. In this work, the link between inferred metallicity and
assumed cloud properties is the thermal profile of atmosphere and interior.
Therefore, we perform coupled atmosphere, interior, and evolution calculations.
The atmosphere model includes clouds in a much simplified manner; it includes
long-wave absorption but neglects shortwave scattering. Within that model, we
show that optically thick, high clouds have negligible influence, whereas
deep-seated, optically very thick clouds can lead to warmer deep tropospheres
and therefore higher bulk heavy element mass estimates. For the young hot
Jupiter WASP-10b, we find a possible enhancement in inferred metallicity of up
to 10% due to possible silicate clouds at $sim$0.3 bar. For WASP-39b, whose
observationally derived metallicity is higher than predicted by cloudless
models, we find an enhancement by at most 50%. However, further work on cloud
properties and their self-consistent coupling to the atmospheric structure is
needed in order to reduce uncertainties in the choice of model parameter
values, in particular of cloud opacities.

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