Linear and circular polarization of comet C/2009 P1 (Garradd)

• Published in: Earth, planets, and space planets, and space, 2013-01, Vol.65 (10), p.1151-1157
• Main Authors: Kiselev, N. N., Rosenbush, V. K., Afanasiev, V. L., Kolesnikov, S. V., Zaitsev, S. V., Shakhovskoy, D. N.
• Format: Article
• Language: English
• Subjects: Circular polarization; Comets; Continuums; Earth; Earth and Environmental Science; Earth Sciences; Geology; Geophysics/Geodesy; Linear polarization; Observatories; Russia; Telescopes
• ISSN: 1343-8832; 1880-5981
• DOI: 10.5047/eps.2013.05.014

We report measurements of linear and circular polarization for the recent comet C/2009 P1 (Garradd) during its approach to the Earth in 2011–2012. Aperture photoelectric observations were carried out on July 29, 2011-April 22, 2012 in the R and WR wide-band filters at the 2.6-m telescope of the Crimean Astrophysical Observatory (Ukraine). Spectropolarimetric measurements of linear polarization in the range 3800–8000 Å and imaging circular polarimetry in the comet continuum filter ( λ 0 = 6840/90 Å) were also carried out with the SCORPIO-2 focal reducer at the 6-m telescope of the Special Astrophysical Observatory (Russia) on February 2-April 21, 2012. The degree of polarization of light scattered by comet Garradd changes from −2.2 ± 0.2% to 4.9 ± 0.2% at phase angles 13.7° and 35.9°, respectively. These values are in a good agreement with those for dusty comets at the respective phase angles. Left-handed (negative) circular polarization of comet Garradd in the continuum filter was identified. The values of Pc vary noticeably over the coma in the range from −0.03 to −0.08% and from −0.05 to −0.3% on February 14 and April 21, respectively. These results confirm our previous conclusion that the observed circular polarization for comets is predominantly left-handed.