UBVRI-POLARIMETRY OF ASTEROID 4179-TOUTATIS

UBVRI polarimetric observations of NEA 4179 Toutatis were carried out at the Crimean Astrophysical Observatory for six nights in December 19 92-January 1993. Phase curves of polarization over the phase angle ran ge 15.8-51.4 degrees were obtained in each photometric band. Spectral dependences of positive polarization, polarimetric slope h, and invers ion angle alpha(inv) in UBVRI wavelength range were obtained for the f irst time. The degree of the linear positive polarization decreases wi th the increase of wavelength supporting the inversion effect of the p olarization spectral dependence of S-type asteroids. The obtained obse rvation data show a fact unknown for asteroids before-the presence of Toutatis polarization unconnected with the scattering plane. For the f irst time the polarimetric estimate of geometric albedo P-v, = 0.13 wa s obtained. Along with other data this value points out that Toutatis is an S-type asteroid having a tentative size of about 3 km. (C) 1995 Academic Press, Inc.