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Paper: Polarimetry of Comets in the Near-IR
Volume: 343, Astronomical Polarimetry: Current Status and Future Directions
Page: 192
Authors: Kelley, M.S.; Woodward, C.E.; Jones, T.J.
Abstract: We present near-IR (2.2 μm) imaging polarimetry for seven recent comets. This data, and previous measurements of comets C/1995 O1 (Hale-Bopp) and 1P/Halley, yield a trend in polarization versus phase angle that is typically 1 - 2% higher in the near-IR than in the visual. We also ̅nd that comets divide into two classes at phase angles greater than 30° based on their polarization. These classes are associated with the presence or absence of mid- IR silicate emission. Using previously published comet Hale-Bopp polarization data as an example, we show the polarization at 40° phase angle varies by a factor of 1.6 from 0.3 to 2.2 μm. This weak wavelength dependence indicates that the polarization is not strongly sensitive to grain size by a wavelength of 2.2 μm suggesting the grains/aggregates must be at least 1 μm in size.
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