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Published January 20, 2016 | Published + Accepted Version + Erratum
Journal Article Open

A Multiple Scattering Polarized Radiative Transfer Model: Application to HD 189733b


We present a multiple scattering vector radiative transfer model that produces disk integrated, full phase polarized light curves for reflected light from an exoplanetary atmosphere. We validate our model against results from published analytical and computational models and discuss a small number of cases relevant to the existing and possible near-future observations of the exoplanet HD 189733b. HD 189733b is arguably the most well observed exoplanet to date and the only exoplanet to be observed in polarized light, yet it is debated if the planet's atmosphere is cloudy or clear. We model reflected light from clear atmospheres with Rayleigh scattering, and cloudy or hazy atmospheres with Mie and fractal aggregate particles. We show that clear and cloudy atmospheres have large differences in polarized light as compared to simple flux measurements, though existing observations are insufficient to make this distinction. Futhermore, we show that atmospheres that are spatially inhomogeneous, such as being partially covered by clouds or hazes, exhibit larger contrasts in polarized light when compared to clear atmospheres. This effect can potentially be used to identify patchy clouds in exoplanets. Given a set of full phase polarimetric measurements, this model can constrain the geometric albedo, properties of scattering particles in the atmosphere, and the longitude of the ascending node of the orbit. The model is used to interpret new polarimetric observations of HD 189733b in a companion paper.

Additional Information

© 2016. The American Astronomical Society. Received 2015 July 13; accepted 2015 December 1; published 2016 January 20. We thank David Crisp and Renyu Hu for several insightful comments. The paper also greatly benefited from the anonymous referee's reviews. This research was supported in part by the Presiden't and Director's Fund at Caltech and by the NAI Virtual Planetary Laboratory grant from the University of Washington to the Jet Propulsion Laboratory and California Institute of Technology. Part of the research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. X.Z. was supported by the Bisgrove Scholar Program at the University of Arizona.


Pushkar Kopparla et al 2018 ApJ 862 176

Attached Files

Published - Kopparla_2016_ApJ_817_32.pdf

Accepted Version - 1512.02308.pdf

Erratum - pdf


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