V photometry of Titania, Oberon, and Triton
1989; Elsevier BV; Volume: 77; Issue: 2 Linguagem: Inglês
10.1016/0019-1035(89)90088-2
ISSN1090-2643
AutoresJ. D. Goguen, Heidi B. Hammel, R. H. Brown,
Tópico(s)Atmospheric Ozone and Climate
ResumoV filter photometry with the 2.2-m University of Hawaii telescope on Mauna Kea obtained during 1982–1983 is analyzed to determine the phase angle and orbital brightness variations of Titania, Oberon, and Triton. The unit distance opposition magnitudes and phase coefficients (α < 3°) are Titania, V(1,0) = 1.016 ± 0.042, β = 0.102 ± 0.021 mag/deg; Oberon, V(1,0) = 1.231 ± 0.035, β = 0.103 ± 0.018 mag/deg; Triton V(1,0) = −1.236 ± 0.041; β = 0.027 ± 0.035 mag/deg. The phase coefficients for Titania and Oberon are comparable to those observed for asteroids at similar small phase angles. Measurements made at α = 0.°06 show an ≈0.2-mag additional increase in brightness similar to that reported in the near-infrared by R. H. Brown and D. P. Cruikshank ((1983), Icarus 55, 83–92). The small phase coefficient for Triton indicates the light may not be scattered from a low-albedo, porous regolith, but suggests a high-albedo surface, a significant atmosphere, or a smooth surface, e.g., an ocean. Orbital lightcurves are less than 0.1 mag in amplitude for Titania, Oberon, and Triton. The Titania data agree well with photometry at phase angles ≥0.°8 from the Voyager 2 imaging experiment (J. Veverka, P. Thomas, P. Helfenstein, R. H. Brown, and T. V. Johnson, 1987, J. Geophys. Res. 92, 14,895–14,904).
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