Photometry studies of comets at the Klet Observatory

V. Vanysek (2), M. Tichy (1), J. Ticha (1), Z. Moravec (1)
(1)Klet' Observatory, Zatkovo nabrezi 4
CZ-370 01 Ceske Budejovice, Czech Republic
e-mail :
(2) Astronomical Institute of the Charles University, Svedska 8,
150 00 Praha 5, Czech Republic

Abstract. The preliminary results of the comet surface photometry performed in the framework of the small bodies programme of the Klet Observatory are discussed. The integrated brightness of the tail of comet 122P/de Vico has been used for the determination of the dust flow characteristics in the tail. It is shown, that in the dusty tail near coma, where the contribution of small "fluffy" and unstable dust particles to the surface brightness of the tail is substantial, the decrease of integrated brightness with distance indicates effects of some kind of disintegration mechanism. The apparent lifetime of grains inferred from the tail photometry is less than one day at the heliocentric distance 1 AU. This effect might be caused either by sublimation or by electrostatic charge disruption of grains, and even the albedo change should be considered.

Since the narrow streams are presented on the tail images of 122P/de Vico obtained with a R filter, a substantial contribution of the ionized molecular species must be considered as another alternative. Among the most abundant ions of the plasma tail are CO+ and H2O+. The contribution of each of these species to the ion tail brightness in the red region must be considered. Nevertheless, the discussed method for the determination of the dissipation coefficient may also be applied here for the ion tail. In such a case the effective lifetime of these species at heliocentric distance 1 AU, is significantly shorter that 105 s. Preliminary analysis of the brightness distribution in the coma of 19P/Borrelly indicates that a population of larger dust grains for which mi <= 1 dominates there.

keywords:comets - 19P/Borrelly - 122P/de Vico - cometary dust

Contrib. Astron. Obs. Skalnate Pleso 30 (2000), 5-11
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