Abstract
Context. The study of distant comets, which are active at large heliocentric distances, is important for a better understanding of their physical properties and mechanisms of long-lasting activity.
Aims. We analyzed the dust environment of the distant comet C/2014 A4 (SONEAR), with a perihelion distance near 4.1 au, using comprehensive observations obtained by different methods.
Methods. We present an analysis of spectroscopy, photometry, and polarimetry of comet C/2014 A4 (SONEAR), which were performed on November 5–7, 2015, when its heliocentric distance was 4.2 au and phase angle was 4.7°. Long-slit spectra and photometric and linear polarimetric images were obtained using the focal reducer SCORPIO-2 attached to the prime focus of the 6 m telescope BTA (SAO RAS, Russia). We simulated the behavior of color and polarization in the coma presenting the cometary dust as a set of polydisperse polyshapes rough spheroids.
Results. No emission features were detected in the 3800–7200 Å wavelength range. The continuum showed a reddening effect with the normalized gradient of reflectivity 21.6 ± 0.2% per 1000 Å within the 4650–6200 Å wavelength region. The fan-like structure in the sunward hemisphere was detected. The radial profiles of surface brightness differ for r-sdss and g-sdss filters, indicating a predominance of submicron and micron-sized particles in the cometary coma. The dust color (g–r) varies from 0.75 ± 0.05m to 0.45 ± 0.06m along the tail. For an aperture radius near 20 000 km, the dust productions in various filters were estimated as Afρ = 680 ± 18 cm (r-sdss) and 887 ± 16 cm (g-sdss). The polarization map shows spatial variations in polarization over the coma from about −3% near the nucleus to −8% at a cometocentric distance of about 150 000 km. Our simulations show that the dust particles are dominated (or covered) by ice and tholin-like organics. Spatial changes in the color and polarization can be explained by particle fragmentation.
Funder
Ministry of Education and Science of the Russian Federation
SASPRO Programme
VEGA
SAIA Programme
Taras Shevchenko National University of Kyiv
SERB
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
14 articles.
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