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Many cometary coma features are only a few percent above the ambient coma (i.e., the background) and therefore coma enhancement techniques are needed to discern the morphological structures present in cometary comae. A range of image enhancement techniques widely used by cometary scientists is discussed by categorizing them and carrying out a comparative analysis. The enhancement techniques and the...
Efforts to apply a single-scattering polarized radiative transfer code to interpret photopolarimetric measurements of coma dust optical properties in Comet Hale-Bopp corroborate previous photometrically derived conclusions concerning the predominance of small sized particles in Hale-Bopp's coma. Calculations of the degree of linear polarization (DP) as a function of observation phase angle (α) produced...
Narrowband reflectance spectra of the saturnian satellites S VII Hyperion and S IX Phoebe were obtained across the 0.4- to 0.8-μm spectral region. The spectrum of Phoebe shows an absorption feature centered near 0.43 μm superimposed on the UV/blue intervalence charge transfer transition present in the spectrum, similar to absorptions identified in the spectra of C-class asteroids (Vilas et al. 1993b...
New narrowband spectrophotometric data of JVI Himalia support its C-type classification. Two spectra taken on successive nights are rotationally sampled. The new spectra confirm the presence of a weak absorption feature centered near 0.7 μm attributed to oxidized iron in phyllosilicates, products of aqueous alteration. Evaluation of the UBV photometry of JVI Himalia and JVII Elara compared to the...
Incipient attempts to apply a single-scattering polarized radiative transfer code along with planetary atmospheres spectrum synthesis procedures to photometric analyses of coma dust optical properties in Comet Hale–Bopp have lead to results which are consistent with other independent derivations of dust physical properties like particle composition, size, number densities, and ejection speeds. In...
A linear mixing model has been used to separate the high-resolution visible/near-infrared reflectance spectrum of the _Iapetus dark material from the spectra of the leading and trailing sides of Iapetus. A distinct absorption feature centered at 0.67 μm is apparent in the spectrum. A slight inflection covering 0.4 to 0.6 μm and a change in slope near 0.73 μm suggesting the lower wavelength edge of...
We have carefully monitored the radial velocities of 21 bright, solar-type stars for 12 years, None has shown any reflex motion due to a substellar companion to an upper limit of between 1 and 3 Jupiter masses (X sin i) for orbital periods less than 15 years, We can also rule out companions of more than 3 to 10 Jupiter masses (X sin i) at much longer periods based on long-term trends in the radial...
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