POLARIMETRIC OBSERVATIONS OF 4179-TOUTATIS IN 1992 1993/

Our polarimetric measurements of asteroid 4179 Toutatis in 1992 and 19 93 have been reexamined, taking into account careful error analyses of the raw data, The resulting values of the polarization degree P and i ts position angle at wavelengths of 0.42, 0.46, 0.53, 0.65, 0.70, and 0.76 mu m are reported for a range of phase angle, alpha, between 13 d egrees.6 and 93 degrees.7. A weak decrease in P with wavelength has be en found at a alpha greater than or equal to 50 degrees, In addition, a small increase in P with increasing phase angle has been confirmed, i.e., a polarimetric slope of 0.09-0.15% deg(-1). Furthermore, we foun d a time variation of polarization and an occurrence of higher polariz ation in the dark phase of the light curve compiled by J. R. Spencer e t al, (1995, Icarus 117, 71-89), Our polarimetric results plus other a vailable data on 4179 Toutatis have confirmed that 4179 Toutatis is an S-type asteroid with an irregular shape and inhomogeneous surface com posed in part of light-transmitting materials such as a mixture of oli vine and pyroxene. (C) 1997 Academic Press.