DR. HIMADRI SEKHAR DAS

The results of imaging polarimetry of the comet C/2009 P1 (Garradd) at phase angles 28.2o, 28.1o and 21.6o are presented, acquired using the IUCAA Faint Object Spectrograph (IFOSC) mounted on the 2m telescope of IUCAA, Pune, India on 21st and 22nd March 2012 and the ARIES Imaging Polarimeter (AIMPOL) mounted on the 1.04m Sampurnanand Telescope of ARIES, Naintital, India on 23rd May, 2012. Both narrow-band filter (Red: ¿= 0.684µm, ¿¿= 0.009 µm) and broadband filter (Red: ¿= 0.630 µm, ¿¿= 0.120 µm) were used in the observation. Jet activity is observed in the treated intensity map of comet Garradd on March's observation. These jets are mainly towards the solar direction and extends up to 5100 kms from the photocenter. The tailward extension is 1800 kms and seems to be fainter. Like other comets, Garradd shows negative polarization at phase angle 21.6o. The observed linear polarization data of Comet Garradd are compared with other comets observed by different investigators in past at the same phase angles. It has been found that comets 67P/Churyumov-Gerasimenko, 22P/Kopff, 1P/Halley, C/1990 K1 (Levy), 4P/Faye, and C/1995 O1 (Hale-Bopp) were also observed at phase angle close to 28o and comet 47P/Ashbrook-Jackson at 21.6o. The polarization values coming out from the present analysis match well with the results obtained for dusty comets at such phase angles. It is also noticed that the linear polarization of the dust coma shows a high degree of linear polarization at 28o, but not exceptionally high as comet Hale-Bopp. Thus, it may be concluded that the comet Garradd belongs to a dusty comet family.