Polarimetry of Binary Stars and Exoplanets

Polarimetry is a useful diagnostic of asymmetries in both circumstellar environments and binary star systems. Its sensitivity to asymmetries in systems means that it can help to uncover details about system orbital parameters, including providing information about the orbital inclination. Polarimetry can probe the circumstellar and/or circumbinary material as well. A number of significant results on binary systems have been produced by polarimetric studies. One might therefore expect that polarimetry could similarly play a useful role in studies of exoplanets, and a number of possible diagnostics for exoplanets have been proposed. However, the application of polarimetry to exoplanet research is only in preliminary stages, and the difficulties with applying the technique to exoplanets are non-trivial. This review will discuss the successes of polarimetry in analyzing binary systems, and consider the possibilities and challenges for extending similar analysis to exoplanet systems.