H. S. Das,B. J. Medhi, S. Wolf, G. H.-M. Bertrang, P. Deb Roy, A. Chakraborty
Context. 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 2 m 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 1.04 m 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.