2016MNRAS.459L.109B

We present linear polarization observations of the exoplanet system HD 189733 made with the HIgh Precision Polarimetric Instrument (HIPPI) on the Anglo-Australian Telescope (AAT). The observations have higher precision than any previously reported for this object. They do not show the large amplitude polarization variations reported by Berdyugina et al. Our results are consistent with polarization data presented by Wiktorowicz et al. A formal least squares fit of a Rayleigh-Lambert model yields a polarization amplitude of 29.4±15.6 parts per million. We observe a background constant level of polarization of ∼55-70 ppm, which is a little higher than expected for interstellar polarization at the distance of HD 189733.