2009ApJ...696.1116W

Using the POLISH instrument, I am unable to reproduce the large-amplitude polarimetric observations of Berdyugina et al. to the >99.99% confidence level. I observe no significant polarimetric variability in the HD 189733 system, and the upper limit to variability from the exoplanet is ΔP < 7.9x10^–5 with 99% confidence in the 400-675 nm wavelength range. Berdyugina et al. report polarized, scattered light from the atmosphere of the HD 189733b hot Jupiter with an amplitude of two parts in 10⁴. Such a large amplitude is over an order of magnitude larger than expected given a geometric albedo similar to other hot Jupiters. However, my nondetection of polarimetric variability phase-locked to the orbital period of the exoplanet, and the lack of any significant variability, shows that the polarimetric modulation reported by Berdyugina et al. cannot be due to the exoplanet.