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Mapping clouds of exoplanets

Antonio García Muñoz

Accurate visible-wavelength, broadband photometry of spatially unresolved exoplanet + star systems is setting key constraints on various aspects of close-in exoplanet atmospheres (geometric albedos, peak brightness offsets) through the investigation of planetary phase curves [1-3]. To date, this is the approach that has been enabled for a handful of exoplanets by COROT and Kepler. In the incoming years, CHEOPS, PLATO and TESS will greatly expand the number of available exoplanet phase curves, thus allowing for comparative studies amongst a larger planet sample. A theoretical framework to investigate such phase curves and the information contained in them is still missing. We have set out to establish such a framework, and to make the connection between the fundamental properties of exoplanet atmospheres (cloud spatial distribution, optical depth, cloud particle scattering properties) and observable phase curves. Our framework relies on a recently devised backward Monte Carlo algorithm [4-5] that solves the full radiative transfer problem in the three-dimensional atmosphere for user-specified atmospheric configurations, i.e. without assuming Lambertian reflection of the planet or similarly simplified treatments. The algorithm is ideally suited for this problem because it computes the phase curves of inhomogeneous planets without any computational overhead with respect to the solution for homogeneous planets. In the presentation, we show which atmospheric properties could be derived from exoplanet phase curves, and emphasize possible degeneracies between key atmospheric parameters. We use our results to explore the parameter space that future exoplanet GCMs equipped with cloud prediction capacities will need to consider.

2015 March 17, 14:30

Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia