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Polarization and brightness opposition effects for the E-type Asteroid 64 Angelina |
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| Authors: | Vera K Rosenbush Nikolai N Kiselev Klaus Jockers Yuriy S Efimov |
| Institution: | a Main Astronomical Observatory of National Academy of Sciences, Zabolotnoho str. 27, 03680 Kyiv, Ukraine b Institute of Astronomy of Kharkiv National University, Sumskaya str. 35, 61022 Kharkiv, Ukraine c Max-Planck-Institut für Sonnensystemforschung, D-37191 Katlenburg-Lindau, Germany d Crimean Astrophysical Observatory, Nauchny, Ukraine |
| Abstract: | We present new polarimetric and photometric observations of the high-albedo Asteroid 64 Angelina in the UBVRI wavebands at phase angles ranging from 0.43° to 13.02° during oppositions in 1995, 1999, and 2000/2001. The polarization opposition effect has been observed in the form of a sharp peak of negative polarization with amplitude of about −0.4% centered at αmin≈1.8°, which is superimposed on the regular negative polarization branch. The amplitude of the polarization opposition effect appears to be apparition-dependent. Our photometric data confirm the early detected by Harris et al. 1989. Phase relations of high-albedo asteroids: The unusual opposition brightening of 44 Nysa and 64 Angelina. Icarus 81, 365-374] of a very strong and unusually narrow opposition spike, i.e., brightness opposition effect, for Angelina. Thus, 64 Angelina is the first asteroid for which both the polarization opposition effect and the brightness opposition effect have been detected. We observed that the polarization opposition effect as well as the regular negative polarization branch depends on the wavelength of scattered light, but in different manners. In addition, the colors B-V and V-R show little phase-angle dependence, while the color U-B increases with increasing phase angle, thus indicating that the amplitude of the brightness opposition effect is larger in the U band and almost the same in the B, V, and R bands. It appears that all colors indices begin to increase with decreasing phase angle to zero. The composite lightcurve computed with a period of 8.752 h has amplitude of 0.13 magnitude. |
| Keywords: | Asteroids 64 Angelina Polarimetry Photometry |
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