Vera Rosenbush

POLARIZATION PROPERTIES OF THE GALILEAN SATELLITES OF JUPITER: OBSERVATIONS AND PRELIMINARY ANALYSIS

We present new, detailed polarimetric measurements of the Galilean satellites of Jupiter with U, B, V , and R -lters at phase angles ranging from 12i to nearly 0i. The polarization phase curves of Io, Europa, and Ganymede in the B, V , and R -lters clearly show the presence of the polarization opposition e†ect in the form of a sharp peak of negative polarization centered at a very small phase angle of and 0i.6E0i.7 superimposed on the regular negative polarization branch. This phase angle is comparable to the width of the spikelike photometric opposition e†ect observed for Europa, thus indicating that both opposition phenomena are likely to be produced by the coherent backscattering mechanism. The U -lter values of for Io and Europa are close to 0.60% and 0.47%, respectively, and exceed the respective BV R o P min o values by a factor of almost 2. The BV R polarization for the trailing hemispheres of Io, Europa, and, especially, Ganymede is systematically stronger than for the respective leading hemispheres. For Callisto, the leading hemisphere polarization is signi-cantly stronger than for the trailing hemisphere. The inver- sion angles for Io, Europa, and Ganymede are nearly wavelength independent and close to 10i.0, 8i.6, and respectively. The inversion angle for the trailing hemisphere of Callisto is also wavelength inde- 8i.8, pendent and is in the range of 12iE13i. Subject headings: minor planets, asteroids E planets and satellites: individual (Jupiter) E polarization E radiative transfer

Photometric and Polarimetric Opposition Phenomena Exhibited by Solar System Bodies

Ground-based and spacecraft observations of atmosphere less solar system bodies (planets, satellites, planetary rings, and asteroids) and cometary and interplanetary dust particles have provided a wealth of new photometric and polarimetric data over a wide range of phase angles and wavelengths. This chapter reviews the progress in the study of the photometric and polarimetric phase effects observed near opposition. We also present the results of recent polarimetric observations of the Galilean satellites of Jupiter, Iapetus, and the asteroid 64 Angelina at very small phase angles. Analyses of the available data allow us to determine the parameters of the brightness and polarization opposition effects and investigate correlations between them. The results obtained may form the observational basis for detailed theoretical modeling and interpretation of the phase effects.

Weak localization of electromagnetic waves and opposition phenomena exhibited by high-albedo atmosphereless solar system objects

The totality of new and previous optical observations of a class of high-albedo solar system objects at small phase angles reveals a unique combination of extremely narrow brightness and polarization features centered at exactly the opposition. The specific morphological parameters of these features provide an almost unequivocal evidence that they are caused by the renowned effect of coherent backscattering.

Circular polarization in comets : Observations of Comet C/1999 S4 (LINEAR) and tentative interpretation

Abstract Comet C/1999 S4 (LINEAR) was exceptional in many respects. Its nucleus underwent multiple fragmentations culminating in the complete disruption around July 20, 2000. We present circular polarization measurements along the cuts through the coma and nucleus of the comet during three separate observing runs, in June 28–July 2, July 8–9, and July 21–22, 2000. The circular polarization was detected at a rather high level, up to 0.8%. The left-handed as well as right-handed polarization was observed over the coma with the left circularly polarized light systematically observed in the sunward part of the coma. During our observations the phase angle of the comet varied from 61 up to 122°, which allowed us to reveal variations of circular polarization with the phase angle. Correlation between the degree of circular polarization, visual magnitude, water production rate, and linear polarization of Comet C/1999 S4 (LINEAR) during its final fragmentation in July 2000 was found. The mechanisms that may produce circular polarization in comets and specifically in Comet C/1999 S4 (LINEAR) are discussed and some tentative interpretation is presented.

Anomalous wavelength dependence of polarization of Comet 21P/Giacobini-Zinner

Abstract Results of CCD imaging and aperture polarimetry of Comet 21P/Giacobini-Zinner and Comet C/1989 U5 (Linear) are presented. Observations were carried out with the 2-m telescope of Pik Terskol Observatory and with the 0.7-m telescope of Kharkov State University in November 1998 and January 1999. The new observations and published data indicate an anomalous spectral dependence of polarization of Giacobini-Zinner, namely, a negative wavelength gradient of the degree of polarization. It is shown that this effect is not caused by the presence of molecular emission in the pass band of the employed filter. The uncommon spectral trend of polarization of Comet Giacobini-Zinner may be caused by a large content of organic matter in its dust or an overabundance of large particles as compared to the other comets.

Comparative Study Of The Dust Polarimetric Properties In Split And Normal Comets

Our polarimetric database contains six comets, C/1975 V1 (West), 16P/Brooks 2,C/1988 A1 (Liller), D/1996 Q1 (Tabur), C/1999 S4 (LINEAR), and C/2001 A2(LINEAR), which can be related to the group of split comets. Comets West, S4(LINEAR) and A2 (LINEAR) were observed during splitting. We compare thepolarimetric measurements of the dust particles in these comets, sometimes togetherwith available photometric and colorimetric data, with those in normal comets. Weconclude that there is no significant evidence for differences of polarization betweentidally split comets (e.g., Brooks 2), dissipating comets (e.g., Tabur), non-tidally splitcomets (e.g., West) and normal comets. The total disintegration of Comet S4 (LINEAR), however, did produce significant changes in the observed properties of dust.

Polarimetric and Photometric Observations of Split Comet C/2001 A2 (LINEAR)

We present the results of polarimetric and photometric observations of split Comet C/2001 A2 (LINEAR), which were obtained at the 70-cm telescope of the Astronomical Observatory of Kharkiv National University between 30 June and 31 July 2001. The brightest fragment of the comet, nucleus B, was observed. Eight narrowband cometary filters in the continuum and in emission bands and a wideband red filter have been used. The comet was observed through apertures of 88, 33, and 19 arcsec. Polarization phase curves were obtained for the continuum and for the first time, for NH2(0, 7, 0) emission. The degree of polarization of the light scattered by the dust decreases with the increase of aperture size. An important temporal variation of the polarization with a rotation of the polarization plane was observed at two phase angles (26.5° and 36.2°). Molecular column densities and production rates of CN, C2, C3, and NH2 species are calculated in the framework of the Haser model. A comparative analysis of the temporal variations of the visual magnitudes, gas and dust production rates, dust color and polarization are presented.

Polarimetry of major Uranian moons at the 6-m telescope

We present the results of polarimetric observations of the icymoons of Uranus (Ariel, Titania, Oberon, and Umbriel) performed at the 6-m BTA telescope of the SAO RAS with the SCORPIO-2 focal reducer within the phase angle range of

Polarization and brightness opposition effects for the E-type Asteroid 64 Angelina

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