1 Introduction

A very important part of the evolution of the solar system relates to the evolution of the minor planets. Amongst other characteristics, the fundamental attributes of an asteroid are its shape, the parameters that define its rotational motion, its taxonomic class and its possible colour and/or albedo variegation on its surface. Physical properties of asteroids such as their shapes, spin periods and spin axes can help in constructing our knowledge of their collisional evolution (Tedesco & Zappala [1980]; Farinella et al. [1981]; Dermott et al. [1984]).

Lightcurve observations of an asteroid are planned for more than one night to improve the accuracy of the period determination, to define the phase relation and absolute brightness as function of the solar phase angle and to determine possible albedo and colour variegation on the surface. Multiple observations of lightcurves from different aspects as an asteroid orbits provide information about spin period, axis orientation and body shape.

In this paper lightcurves of 40 Harmonia, 45 Eugenia and 52 Europa taken in 1997, for two observing periods are presented, one during September and the other during October, from the observatory of Sierra Nevada, Spain (0.9 m Telescope). Our object is to increase the ecliptic longitude coverage of these asteroids to obtain a larger data base relating to their asteroidal lightcurves in order to improve future work on their rotational and shape properties.

Here, uvby Strömgren photometry for 40 Harmonia, 45 Eugenia and 52 Europa are obtained and used to derive phase coefficients correction, multiple scattering factors, Strömgren and Johnson zero-phase angle magnitudes and colour indices and to determine possible colour variegation of the surface of these asteroids during their rotational cycles. Results for rotational and shape parameters for these asteroids have also been obtained and compared with previous results.