Optical phase curves as diagnostics for aerosol composition in exoplanetary atmospheres

Oreshenko, Maria; Heng, Kevin; Demory, Brice-Olivier (2016). Optical phase curves as diagnostics for aerosol composition in exoplanetary atmospheres. Monthly notices of the Royal Astronomical Society, 457(4), pp. 3420-3429. Oxford University Press 10.1093/mnras/stw133

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Optical phase curves have become one of the common probes of exoplanetary atmospheres, but the information they encode has not been fully elucidated. Building on a diverse body of work, we upgrade the Flexible Modelling System to include scattering in the two-stream, dual-band approximation and generate plausible, three-dimensional structures of irradiated atmospheres to study the radiative effects of aerosols or condensates. In the optical, we treat the scattering of starlight using a generalization of Beer's law that allows for a finite Bond albedo to be prescribed. In the infrared, we implement the two-stream solutions and include scattering via an infrared scattering parameter. We present a suite of four-parameter general circulation models for Kepler-7b and demonstrate that its climatology is expected to be robust to variations in optical and infrared scattering. The westward and eastward shifts of the optical and infrared phase curves, respectively, are shown to be robust outcomes of the simulations. Assuming micron-sized particles and a simplified treatment of local brightness, we further show that the peak offset of the optical phase curve is sensitive to the composition of the aerosols or condensates. However, to within the measurement uncertainties, we cannot distinguish between aerosols made of silicates (enstatite or forsterite), iron, corundum or titanium oxide, based on a comparison to the measured peak offset (41° ± 12°) of the optical phase curve of Kepler-7b. Measuring high-precision optical phase curves will provide important constraints on the atmospheres of cloudy exoplanets and reduce degeneracies in interpreting their infrared spectra.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Heng, Kevin

Subjects:

500 Science
500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

0035-8711

Publisher:

Oxford University Press

Language:

English

Submitter:

Janine Jungo

Date Deposited:

30 Jun 2017 16:28

Last Modified:

30 Jun 2017 16:28

Publisher DOI:

10.1093/mnras/stw133

BORIS DOI:

10.7892/boris.97258

URI:

https://boris.unibe.ch/id/eprint/97258

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