Presentation #109.03 in the session Dusty and Icy Cometary Comae.
We present a study of a unique disk-like comet C/2014 B1 (Schwartz). The data were obtained on January 23–31, 2017 at the 6-m telescope of the SAO and present quasi-simultaneous long-slit spectra and the g- and r-sdss photometric and polarimetric images acquired at phase angle 2°. Below we show the image of the coma, direct and filtered with the low-contrast features revealed, as well as the maps of g–r color and polarization. These comprehensive observations allowed us to build a consistent model of the coma and processes in it.
Our spectral data indicated absence of any emissions. Thus, the observed brightness, color, and polarization were produced by the solar light scattered on the dust particles. Study of the coma morphology revealed two jets originated from the two active sources located near the north and south poles of the nucleus. We derived the brightness profile for the coma and jets with the gradients –1.29 and –1.06, respectively.
We modeled the brightness profile and variations of color and polarization presenting the dust particles as aggregates of several porosities and of radius from 5 to 1280 μm and using an extended version of the RT–CB code (Muinonen, 2004, Waves Random Media, 14, 365) with the static structure factor correction (Cartigny et al. 1986, J. Heat Transf., 108, 608). The submicron monomers had a core composed of a mixture of silicates and organic (to reproduce the red color) and a mantle of H2O and CO2 ices (to reach large values of negative polarization). The best-fit porosity of particles was in the range 0.975–0.9875. The modeling showed that the combination of color (0.7m) and polarization (–1.5%) observed for the near-nucleus area could be reached only for large, ~1 mm, particles. The combination of color (0.3m–0.4m) and polarization (–7%) observed in the outer coma can be reproduced by particles of radii 10–20 μm, indicating fragmentation of the dust particles on their way from the nucleus. Considering that mm-sized particles sequentially break up, finally generating 10-μm particles, we could also reproduce the observed =brightness profiles for both jets and coma, thus providing a consistent picture of the dust characteristics and fragmentation in the coma of comet Schwartz.