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

TL;DR

This study presents imaging polarimetry and spectropolarimetry of comet C/2013 R1 (Lovejoy), revealing polarization characteristics of dust and gas emissions, and their spatial and spectral variations, contributing to understanding cometary dust properties.

Contribution

First detailed polarimetric analysis of comet C/2013 R1 (Lovejoy) across multiple wavelengths and spatial regions, highlighting dust and gas polarization behavior.

Findings

Polarization degree of ~17-19% in dust continuum filters.

Polarization increases with wavelength in the nucleus region.

Depolarization observed in gas emission lines, especially C2.

Abstract

We have obtained imaging polarimetry of the comet C/2013 R1 (Lovejoy) with 2-Channel-Focal-Reducer Rozhen instrument at 2m Ritchey-Chr\'etien-Coud\'e telescope of the Bulgarian National Astronomical Observatory Rozhen in two dust continuum filters covering wavelength intervals clear from molecular emissions and centred at $4430\AA$ in (blue filter) and at $6840\AA$ in (red filter). In imaging mode we measured the degree of linear polarisation $17.01\pm0.09$% in the blue and $18.81\pm0.02$% 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 C$_2$ emission band, which shows a polarisation of $6.0\pm1.1$%.