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 1992-January 1993. Phase curves of polarization over the phase angle range 15.8-51.4° were obtained in each photometric band. Spectral dependences of positive polarization, polarimetric slope h, and inversion angle α _inv in UBVRI wavelength range were obtained for the first time. The degree of the linear positive polarization decreases with the increase of wavelength supporting the inversion effect of the polarization spectral dependence of S-type asteroids. The obtained observation data show a fact unknown for asteroids before—the presence of Toutatis polarization unconnected with the scattering plane. For the first time the polarimetric estimate of geometric albedo p_v = 0.13 was obtained. Along with other data this value points out that Toutatis is an S-type asteroid having a tentative size of about 3 km.