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P. Rousselot (Observatoire de Besancon / UMR-CNRS 6091, France), A.C. Levasseur-Regourd (Université Paris VI / Aéronomie CNRS-IPSL, France)
Knowing the surface properties of Kuiper Belt Objects is mandatory to assess the physical processes that shaped their evolution. Before space missions take place, these properties are approached by scattered (solar) light observations, and more precisely by polarimetric observations. Although long integration times on large instruments are required, the polarimetric data are normalized and thus only depend upon the phase angle, the wavelength, and the physical properties of the object [1]. We present new polarization and brightness observations, obtained on the Scattered Disk Object 1999~TD10 with FORS1 at the ESO 8.2-m VLT. The observations were conducted in two colors (R and V bands), for phase angles ranging from 0.7\circ to 3.1\circ (November and December 2003). The trend in brightness can be compared with previous observations of the same object [2, 3]. The polarization is significantly negative at small phase angles, most likely because of multiple scattering mechanisms, as previously noticed for Ixion [4]. A wavelength dependence of the polarization is observed for the first time on a KBO, with a polarization more negative in R than in V. Such a result provides constraints on the physical properties of the surface, which could be derived through elaborated numerical and laboratory simulations.
[1] A.C. Levasseur-Regourd, Earth, Moon Planets, 92, 337-343 (2003). [2] P. Rousselot et al., Astron. Astrophys. 407, 1139-1147 (2003). [3] B. Mueller et al., Icarus, in press (2004). [4] H. Boehnardt et al., Astron. Astrophys. Letters 415, L21, (2004).
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.