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Context. We analyze the results of our comprehensive observations of the high-perihelion comet C/2014 B1 (Schwartz) with stable disk-shaped coma and jets in order to study its nature. Aims. The main objective of our study is to obtain new observational results for a unique disk-like comet C/2014 B1 (Schwartz) with a perihelion distance of 9.56 au. Methods. Quasi-simultaneous long-slit spectra, as well as photometric and polarimetric images with g-sdss and r-sdss filters, were acquired with the 6m telescope of the Special Astrophysical Observatory on 2017 January 23. The BVR-band photometry of the comet was also performed at the 2m telescope of the Peak Terskol Observatory on 2017 January 31. We modeled the dynamics of the jets and the behavior of the color and polarization in the coma considering the dust as aggregated large particles. Results. We did not reveal any emissions in the spectra. The positions of two jets oriented along the position angles of 179 and 350 and the disk-like shape of the coma have remained unchanged for more than 4 yr. The most realistic model able to explain jets of such stable orientation includes the existence of two active sources located near the north and south poles of the rotating nucleus whose diameter was determined to be between 7.6 and 12.2 km depending on the albedo, of namely between 0.1 and 0.04, respectively. The high activity of the comet is characterized by the high dust production Af which varied from 4440 to 3357 cm between 2017 January 23 and 31. A significant difference between the radial surface brightness profiles of the jets and the ambient (undisturbed by the jets) coma is found. The color of the jet structures is much redder than that of the ambient coma, and the nucleus has a very red color, V - R=0.93m±0.19m. There are spatial variations of the color and polarization over the coma and jets. Conclusions. The observed trends in color and polarization, as well as the brightness profiles, can be explained by the fragmentation of aggregated particles formed by CO2/H2O ices, silicates, and organics, which are of ~1 mm in radius near the nucleus and ~10 µm in radius at the periphery of the coma. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]