COMETS OKAZAKI-LEVY-RUDENKO (1989-XIX) AND LEVY (1990-XX) - POLARIMETRY AND STELLAR OCCULTATIONS

The results of polarimetric observations of comets Okazaki-Levy-Rudenk o 1989 XIX and Levy 1990 XX and two stellar occultations by the latter comet are presented. Wavelength, phase angle, and aperture dependence s of polarization are discussed. During the outburst activity of comet Levy variations of the polarization parameters were registered. From a stellar occultation by comet Levy the optical thickness of the coma is found to be T = 0.40 +/- 0.06 at a distance of 3500 km from the nuc leus on the sunward side. The measured light flux, negative polarizati on, and high optical thickness in the observed regions of coma assume the presence in the coma of either a large number of Rayleigh particle s with addition of some large ones, or a large number of absorbing flu ffy grains on which multiple reflections of light are possible, or the ir mixture. Analysis of the polarimetric observations of occulted star s by the comet indicates the presence of oriented nonspherical particl es in the coma. The observations of stellar occultations are seen to b e useful probes of oriented and Rayleigh particles. (C) 1994 Academic Press, Inc.