Rosenbush V. Spectral and photometric features of selected comets

The thesis is dedicated to study of selected comets. The results of spectral (7 comets) and photometric (11 comets) observations are the basis of this investigation. The physical characteristics of a coma, tail, and nucleus, such as column density and production rate of gas and dust in the cometary atmosphere, relative intensities of the band sequences for different molecules and ions, dust color, particle albedo, optical thickness of dust, effective radius and rotation period of the nucleus, etc., are determined. Three split comets C/1975 V1 (West), D/1996 Q1 (Tabur), and С/2001 А2 (LINEAR) have been studied and the observational evidences of inhomogeneity of the parent nucleus of comets West and Tabur are found. For the first time, it was found that the NH2 coma was elongated perpendicularly to the comet radius-vector. The abnormal abundances of some species observed in comets West, 21Р/Giacobini-Zinner, and А2 (LINEAR) were revealed from the analysis of gas and dust production rates in the cometaryatmospheres and their heliocentric dependences. From stellar occultations by comets С/1990 K1 (Levy), С/1995 O1 (Hale-Bopp) and 1P/Halley (from the literary data) the optical thickness of the dust coma and its spectral and spatial dependence is found. The conclusion is made that the diagram of [(UC-BC)-(BC-RC)] may be used for diagnostics of belonging comets to different taxonomical classes. Finally, a generalization and comparative analysis of the physical and dynamical characteristics of the studied comets was performed. It is shown that the physical properties of comets are a very important supplement to their dynamical characteristics when the cosmogonical problems are considered.