We report observations of color in the inner coma of Comet C/2013 UQ4 (Catalina) with the broadband B and R filters. We find significant temporal variations of the color slope, ranging from -12.67 ± 8.16% per 0.1 m up to 35.09 ± 11.70% per 0.1 m. It is significant that the comet changes color from red to blue over only a two-day period. Such dispersion cannot be characterized with an average color slope. We also observe Comet C/2013 UQ4 (Catalina) in infrared using Spitzer and find no significant CO/CO 2 gaseous species in its coma. Therefore, we classify Comet C/2013 UQ4 (Catalina) as a dust-rich comet and attribute the measured color slope to its dust. We analyze the color slope using the model of agglomerated debris particles and conclude that the C/2013 UQ4 coma was chemically heterogeneous, consisting of at least two components. The first component producing the bluest color is consistent with Mg-rich silicates.There are three different options for the second component producing the reddest color. This color is consistent with either Mg-Fe silicates, kerogen type II, or organic matter processed with a low dose of UV radiation.

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Abstract. We present the analysis of the polarimetric and spectral data obtained for the dynamically new comet C/2012 J1 (Catalina) when it was at a distance of 3.17 AU from the Sun. The observations were made at the prime focus of the 6-m BTA telescope using the SCORPIO-2 focal reducer. The map of the distribution of linear polarization in the cometary coma was constructed. The calculated value of linear polarization was on average about −2%. Spectral analysis of the cometary coma allowed us to detect the emission of the CN molecule in the (0-0) band. The gas production rate was derived using the Haser model and amounted to 3.7 × 10 23 molecules per second.

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