Polarimetry of comets 67P/Churyumov–Gerasimenko, 74P/Smirnova–Chernykh, and 152P/Helin–Lawrence⋆
1 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK
e-mail: email@example.com; firstname.lastname@example.org
2 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking RH5 6NT, UK
3 INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
4 Max-Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
5 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
6 Department of Physics, University of Helsinki, PO Box 64, Gustaf Hällströmin katu 2a, 00014 Helsinki, Finland
7 Finnish Geospatial Research Institute FGI, Geodeetinrinne 2, 02430 Masala, Finland
8 The Centre for Planetary Sciences at UCL/Birkbeck, Gower Street, London WC1E 6BT, UK
Received: 4 November 2015
Accepted: 9 May 2016
Aims. Polarimetric characteristics of comets at large heliocentric distances is a relatively unexplored area; we extend the idea by adding and analysing the data for three Jupiter family comets (JFCs).
Methods. With the FORS2 instrument of the ESO VLT, we performed quasi-simultaneous photometry and polarimetry of three active JFCs 67P/Churyumov-Gerasimenko, 74P/Smirnova-Chernykh, and 152P/Helin-Lawrence.
Results. We obtained in total 23 polarimetric measurements at different epochs, covering a phase-angle range ~1°−16° and heliocentric distances from 3 to 4.6 au. From our observations we obtained both colour and polarimetric maps to look for structures in the comae and tails of the comets.
Conclusions. 74P/Smirnova-Chernykh and 152P/Helin-Lawrence exhibit enough activity at large heliocentric distances to be detectable in polarimetric measurements. Polarimetric and colour maps indicate no evidence of dust particle evolution in the coma. From near-infrared spectra we find no evidence of water ice in the coma of comet 152P/Helin-Lawrence.
Key words: polarization / comets: individual: 67P/Churyumov-Gerasimenko / comets: individual: 74P/Smirnova-Chernykh / comets: individual: 152P/Helin-Lawrence
© ESO, 2016