Institution: | Astronomical Institute, National Observatory of Athens, PO Box 20048, Athens 118 10, Greece; School of Physics and Astronomy, University of St. Andrews, St Andrews KY16 9SS; Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain; Osservatorio Astrofisico di Catania, CittáUniversitaria, I-95125, Catania, Italy; Centro Galileo Galilei, Apartado 565, E-38700 Santa Cruz de La Palma, Spain |