Probing disk inhomogeneities using spectropolarimetry in the extreme binary epsilon Aurigae

The ɛ Aurigae system is a single-line spectroscopic binary system that consists of a variable F0 supergiant star and an occulting disk surrounding an unseen object, probably a B star. The eclipse occurs every 27 years and lasts for almost 2 years. Spectral features attributed to the disk exhibit line shifts due to the rotation of the disk that are easily observed in spectra. We obtained 50+ epochs of high dispersion optical spectropolarimetric data from the ESPaDOnS instrument at the Canada-France-Hawaii Telescope before, during, and after the most recent eclipse (2009-2011). We found numerous 3-sigma (or greater) linear polarization features in the spectra and associated these with atomic absorption features also present in the spectra. We observed dramatic changes to polarization and position angles with time during eclipse, particularly around 3^rd contact. The increased polarization could be due to a localized increased number of scatterers.