2015ApJ...813...48W -
Astrophys. J., 813, 48 (2015/November-1)
A ground-based albedo upper limit for HD 189733b from polarimetry.
WIKTOROWICZ S.J., NOFI L.A., JONTOF-HUTTER D., KOPPARLA P., LAUGHLIN G.P., HERMIS N., YUNG Y.L. and SWAIN M.R.
Abstract (from CDS):
We present 50 nights of polarimetric observations of HD 189733 in the B band using the POLISH2 aperture-integrated polarimeter at the Lick Observatory Shane 3-m telescope. This instrument, commissioned in 2011, is designed to search for Rayleigh scattering from short-period exoplanets due to the polarized nature of scattered light. Since these planets are spatially unresolvable from their host stars, the relative contribution of the planet-to-total system polarization is expected to vary with an amplitude of the order of 10 parts per million (ppm) over the course of the orbit. Non-zero and also variable at the 10 ppm level, the inherent polarization of the Lick 3-m telescope limits the accuracy of our measurements and currently inhibits conclusive detection of scattered light from this exoplanet. However, the amplitude of observed variability conservatively sets a 99.7% confidence upper limit to the planet-induced polarization of the system of 60 ppm in the B band, which is consistent with a previous upper limit from the POLISH instrument at the Palomar Observatory 5-m telescope. A physically motivated Rayleigh scattering model, which includes the depolarizing effects of multiple scattering, is used to conservatively set a 99.7% confidence upper limit to the geometric albedo of HD 189733b of Ag< 0.40. This value is consistent with the value Ag = 0.226 ± 0.091 derived from occultation observations with Hubble Space Telescope STIS, but it is inconsistent with the large Ag = 0.61 ± 0.12 albedo reported by Berdyugina et al.
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Journal keyword(s):
dust, extinction - planetary systems - planets and satellites: atmospheres - planets and satellites: individual: HD 189733b - polarization - techniques: polarimetric
Simbad objects:
22
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