Orbital parameters of extrasolar planets derived from polarimetry

TL;DR

This paper develops a theoretical model using Rayleigh scattering physics to interpret polarimetric observations of extrasolar planets, analyzing how various parameters influence polarization curves and assessing the robustness of fitting procedures.

Contribution

It introduces a comprehensive theoretical parameter study for polarimetric analysis of extrasolar planets, including effects of star size and scattering assumptions.

Findings

Polarization curve shapes are similar whether using Lambert sphere or Rayleigh scattering for intensity.

The difference between the two scattering assumptions is negligible for polarization curves.

Host star size significantly affects polarization signals, especially for hot Jupiters orbiting giant stars.

Abstract

Polarimetry of extrasolar planets becomes a new tool for their investigation, which requires the development of diagnostic techniques and parameter case studies. Our goal is to develop a theoretical model which can be applied to interpret polarimetric observations of extrasolar planets. Here we present a theoretical parameter study that shows the influence of the various involved parameters on the polarization curves. Furthermore, we investigate the robustness of the fitting procedure. We employ the physics of Rayleigh scattering to obtain polarization curves of an unresolved extrasolar planet. Calculations are made for two cases: (i) assuming an angular distribution for the intensity of the scattered light as from a Lambert sphere and for polarization as from a Rayleigh-type scatterer, and (ii) assuming that both the intensity and polarization of the scattered light are distributed according to the Rayleigh law. We show that the difference between these two cases is negligible for the shapes of the polarization curves. In addition, we take the size of the host star into account, which is relevant for hot Jupiters orbiting giant stars.