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The Effect of Clouds as an Additional Opacity Source on the Inferred Metallicity of Giant Exoplanets

Status Report From: arXiv.org e-Print archive
Posted: Thursday, November 7, 2019

Anna Julia Poser, Nadine Nettelmann, Ronald Redmer

(Submitted on 4 Nov 2019)

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 ∼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.

Comments: Published: 30 October 2019 in Atmosphere

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Journal reference: Atmosphere (2019), 10, 664

DOI: 10.3390/atmos10110664

Cite as: arXiv:1911.01191 [astro-ph.EP] (or arXiv:1911.01191v1 [astro-ph.EP] for this version)

Submission history

From: Anna Julia Poser [view email]

[v1] Mon, 4 Nov 2019 13:30:09 UTC (400 KB)

https://arxiv.org/abs/1911.01191

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