TITLE: Analysis of gas/dust environment of selected comets

AUTHOR: Luk’yanyk I.V., Astronomical Observatory of Taras Shevchenko National University of Kyiv

ABSTRACT:
The report contains some results of the work within SAIA grant. 
Comets 41P/Tuttle-Giacobini-Kresak and C/2014 A4 (SONEAR) were investigated. 
Spectral, photometric and polarimetric observations of dynamically new comet 
C/2014 A4 (SONEAR) showed a considerable level of activity (extended dust 
coma and tail) at heliocentric distances of 4 AU. Since molecular emissions 
were not detected in the spectra of this comet, it allows one to study 
reflective dust properties without gas emission effect. Some structures 
(e.g., jets) show larger values of polarization than coma (even for the same 
comet). This fact suggests that there are fundamental differences in the size 
and structure of the dust in the jet outflow which can be an indicator 
of inhomogeneities in nucleus. The modeling shows that the specifics 
of the dust in the distant comet C/2004 A4 (SONEAR) is presence of significant 
amount of ice and organics which likely sublimate at the smaller 
heliocentric distances. Also analyze of photometric observations 
of comet 41P/Tuttle-Giacobini-Kresak are made. The colour, normalized 
reflectivity (reddening) of the near nucleus area and dust production rate 
by measuring the Af\rho parameter are calculated. The results of modeling 
the color slope of dust in comet 41P using agglomerated debris particles 
are presented.