Phoebe at True Opposition: Multiwavelength Phase Curves
Verbiscer, Anne J.; French, R. G.; Aguirre, A.;Guijarro, A.; Hoyo, F.; Sanchez, S. F.; Marinoni, S.;Chanover, N. J.; Holtzman, J.; Magazzu, A.;Helfenstein, P.; Martin, J.; Chatzikos, M.;Herbst, T.. Phoebe at True Opposition: Multiwavelength Phase Curves. American Astronomical Society, DPS meeting #38, #69.05; Bulletin of the American Astronomical Society. 2006, Vol. Vol. 38, p.621, p. -2006.
The 2005 opposition of Saturn offered a rare opportunity to observe its satellites at the smallest possible phase angles, including the minimum phase angle, 0.02° established by the angular size of the Sun at Saturn's heliocentric distance. We present solar and rotational phase curves of Phoebe obtained in broadband UBVRI and Stromgren vby filters at six observatories using the Loiano (Bologna, Italy) 1.5 m, Calar Alto (Spain) 2.2 m, Telescopio Nazionale Galileo (Canary Islands) 3.6 m, Apache Point (Sunspot, New Mexico) 3.5 m and 1 m, and the Vatican Advanced Technology (Mt. Graham, Arizona) 1.8 m telescopes. The angular width of Phoebe's opposition effect increases with wavelength, as predicted by coherent backscatter models, and places constraints on physical regolith properties such as particle size and compaction. Around 02:00 UT on 14 January 2005, an anomalous increase ( 20% in U-band) in Phoebe's brightness at the shortest wavelengths was observed at both Loiano and Calar Alto and faded during the subsequent half hour.
The 2005 opposition of Saturn offered a rare opportunity to observe its satellites at the smallest possible phase angles, including the minimum phase angle, 0.02° established by the angular size of the Sun at Saturn's heliocentric distance. We present solar and rotational phase curves of Phoebe obtained in broadband UBVRI and Stromgren vby filters at six observatories using the Loiano (Bologna, Italy) 1.5 m, Calar Alto (Spain) 2.2 m, Telescopio Nazionale Galileo (Canary Islands) 3.6 m, Apache Point (Sunspot, New Mexico) 3.5 m and 1 m, and the Vatican Advanced Technology (Mt. Graham, Arizona) 1.8 m telescopes. The angular width of Phoebe's opposition effect increases with wavelength, as predicted by coherent backscatter models, and places constraints on physical regolith properties such as particle size and compaction. Around 02:00 UT on 14 January 2005, an anomalous increase ( 20% in U-band) in Phoebe's brightness at the shortest wavelengths was observed at both Loiano and Calar Alto and faded during the subsequent half hour.