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R. Furusho (School of Education, Waseda Univ.), H. Kawakita (Kyoto Sangyo Univ.), Y. Ikeda (Genesia co.), T. Kasuga (Soukendai), Y. Sato (Tokyo Univ.), J. Watanabe (National Astron. Obs. of Japan)
We developed the optical polarimetric imager (named ``PICO") for the study on cometary dust grains. In order to avoid the influences on measurements caused by the change in sky conditions, the PICO was designed as a double-beam type polarimeter (for linear polarization). Here we introduce some recent results by PICO for comet C/2002 T7 (LINEAR), C/2001 Q4 (NEAT), 81P/Gehrels 2, and C/2004 Q4 (Machholz) in 2003 --- 2005. Usually I-band (Kron-Cousins) or i'-band (Gunn) filter was used to obtain the images of the reflected sunlight by cometary dust grains (we used some narrow-band filters for a bright comet only). Comet C/2001 Q4 (NEAT) showed a prominent jet feature (higher polarized region) in the map of polarization degree at near its perihelion passage. We discuss on this higher polarized region.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.