Abstract:
We present the optical imaging polarimetric observations of comet C/2009 P1 (Garradd) at
three different phase angles e.g. 28.°2, 28.°1 and 21.°6. The observations were carried out
using the Inter University Centre for Astronomy and Astrophysics (IUCAA) Faint Object
Spectrograph and Camera mounted on Cassegrain focus of the 2m telescope of IGO, IUCAA,
Pune, in Rcomet, R photometric bands, on 2012 March 21 and 22 and Aryabhatta Research
Institute of observational sciencES (ARIES) Imaging Polarimeter mounted on Cassegrain
focus of the 1.04m Sampurnanand Telescope of ARIES, Nainital, in R photometric band, on
2012 May 23. We show the presence of a jet activity in the rotational-gradient-treated image
of comet Garradd at phase angle 28.°1. These jets are mainly oriented towards the Sun and
extended up to ~5100 km from the cometary photocentre. The antisolar extension of the jet
seems to be fainter, which is extended up to~1800 km. It is found that the comet Garradd shows
negative polarization at phase angle 21.°6. The degree of polarization derived for Garradd is in
good agreement with other comets at nearly similar phase angles e.g. comets 67P/Churyumov–
Gerasimenko, 22P/Kopff, 1P/Halley, C/1990 K1 (Levy), 4P/Faye and C/1995 O1 (Hale–Bopp)
at phase angle ~28°, and 47P/Ashbrook–Jackson at phase angle ~21.° 6, respectively. It is also
found that the degree of polarization of dusty coma of comet Garradd at phase angle ~28° is
high but not as high as in the case of comet Hale–Bopp.
