Imaging polarimetry and spectropolarimetry of comet C/2013 R1 (Lovejoy)

Abstract

We have obtained imaging polarimetry of the comet C/2013 R1 (Lovejoy) with 2-Channel-Focal-Reducer Rozhen instrument at 2m Ritchey–Chrétien–Coudé telescope of the Bulgarian National Astronomical Observatory Rozhen in two dust continuum filters covering wavelength intervals clear from molecular emissions and centred at 4430Å in blue filter and at 6840Å in red filter. In imaging mode we measured the degree of linear polarisation 17.01±0.09% in the blue and 18.81±0.02% in the red, which is in a very good agreement with measurements of other comets at the similar phase angle. We have also obtained polarisation maps in both filters. We found a strong correlation between the spatial distribution of the polarisation and the dust colour. Spectropolarimetry of the nucleus region shows an increase of the polarisation with wavelength, and a depolarisation in the spectral regions with gas emission lines, most noticeable in C2 emission band, which shows a polarisation of 6.0±1.1%.