5 Conclusions

Lightcurves of asteroids 10 Hygiea, 241 Germania and 509 Iolanda, obtained during September-October 1996 using uvby Strömgren photometry, are presented. The lightcurves obtained for each of these three asteroids show two maxima and two minima per cycle. No significant tendencies are found in the colour indices of 241 Germania and 509 Iolanda during their rotational phases. However, a slight variation is detected in the the v-b and u-b colour indices of 10 Hygiea during its rotational phase. The values for the sidereal period, the pole and the shape parameters derived for 10 Hygiea are in agreement with previous results. A first estimation for the sidereal period, the pole position and shape of 241 Germania is presented and a value for the synodic period of 509 Iolanda is proposed.

Acknowledgements

This research was partially supported by the Comisión Interministerial de Ciencia y Tecnología under contracts ESP97-1773-C03-01 and ESP97-1798, the Junta de Andalucía and the Dirección General de Enseñanza Superior e Investigación Científica (DGESIC) under project PB98-0499. This research has made use of the Asteroid Photometric Catalogue database. We very gratefully acknowledge the staff of Sierra Nevada Observatory for their help during the run of observations. Acknowledgements are also especially made to M.C. Romero for making available many papers used in this investigation and to V.G. Brown for proofreading. We wish to thank the referee, A. Harris, for his useful comments and suggestions.