Photometry and polarimetry of comet 46P/Wirtanen in the 2018 apparition

• Published in: Monthly notices of the Royal Astronomical Society 2021-05, Vol.503 (3), p.4297-4308
• Main Authors: Rosenbush, Vera, Kiselev, Nikolai, Husárik, Marek, Ivanova, Oleksandra, Luk'yanyk, Igor, Kleshchonok, Valerii, Tomko, Dušan, Kaňuchová, Zuzana, Pit, Nikolai, Antoniuk, Кirill, Karpov, Nikolai, Savushkin, Alexander, Zhuzhulina, Elena
• Format: Article
• Language: English
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stab585

ABSTRACT Extensive photometric and polarimetric observations of comet 46P/Wirtanen within the framework of the international 4*P Coma Morphology Campaign were conducted from 2018 August 16 to 2019 February 13 using five telescopes. Digital processing applied to the direct images of the comet revealed the coma and tail, which varied in shape and size. The jet at the position angle 133.5° was found in the images obtained on 2018 December 7 and 9 in the V and R filters. From modelling the formation of the jet, we calculated the coordinates of the north pole of the nucleus rotation axis, α = 220° ± 10°, δ = –20° ± 8°, and the cometocentric latitude of the active area on the nucleus L = 20° ± 6°. The velocity of matter outflow from this active area was estimated to be 0.5 ± 0.05 km s−1. The dust production Afρ changed from 12 to 88 cm. During our observation period, the coma colour varied from 0.76m to 0.87m and from 0.38m to 0.50m and the reflectivity gradient from 11 to 16.2 per cent per 1000 Å and 5.8 to 15.4 per cent per 1000 Å for the B – V and V–R spectral bands, respectively. The comparison of the dust production rate of comet 46P/Wirtanen until 2018 and our data for 2018 apparition confirmed its great decrease. The degree of polarization of comet 46P was measured at the phase angles from 27° to 37°. In order to reliably retrieve the polarimetric class of comet 46P, observations at large phase angles are required.