Earth Planets Space, Vol. 65 (No. 10), pp. 1151-1157, 2013
N. N. Kiselev1, V. K. Rosenbush1, V. L. Afanasiev2, S. V. Kolesnikov3, S. V. Zaitsev1, and D. N. Shakhovskoy4
1MAO NAS Ukraine, 27 Zabolotnoho str., 03680 Kyiv, Ukraine
2Special Astrophysical Observatory, RAS, Nizhnii Arkhyz, Karachai-Cherkessian Republic, 357147 Russia
3Observatory of the Odessa National University, Shevchenko Park, 65014 Odessa, Ukraine
4Crimean Astrophysical Observatory, Nauchny, 98409, Crimea, Ukraine
(Received October 31, 2012; Revised May 23, 2013; Accepted May 24, 2013; Online published October 24, 2013)
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 (λ0 = 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.
Key words: Comets, comet C/2009 P1 (Garradd), linear and circular polarization.