Asteroid polarimetric observations using the Torino UBVRI photopolarimeter

A long-term project of polarimetric observations of minor planets has been carried out since 1995 at the 2.15-m telescope of the El Leoncito Observatory (San Juan, Argentina) using the Torino photopolarimeter. We present here an updated summary of the results, including many measurements obtained during the most recent observing runs. The main purpose of the observations has been to obtain albedo estimates and compare them with previous IRAS radiometric determinations, mainly for objects having small (<50 km) IRAS diameters. Another field of investigation is the measurement of the degree of linear polarization at very small phase angles (less than 1°). The latter observations can be a useful input for modern theoretical models of light scattering from asteroid surfaces. In general, we have obtained a wealth of new results, including objects exhibiting a peculiar polarimetric behavior.