Shape and size of asteroid 4 Vesta: Speckle interferometry and polarimetry

Abstract Speckle interferometric data for Vesta and diffraction-limited images of Vesta's disk are presented for three measurements near the opposition of 1988. It is argued that polarimetric data can be utilized to estimate a contribution of albedo features to Vesta's lightcurve, and thus to derive the geometric component of the lightcurve. The analysis of speckle data and polarimetric data together with the results of simulation of speckle interferometry for Vesta enables us to conclude that Vesta must have an almost equilibrium shape, with the axes ratio a / b close to unity.