Affiliation: | European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Mu¨nchen, Germany,;Universitàdegli Studi di Milano, Dipartimento di Fisica, via Celoria 16, 20133 Milano, Italy,;Max-Planck-Institut fu¨r Kernphysik, Postfach 103980, D-69117 Heidelberg, Germany,;Laboratoire d'Astronomie Spatiale, BP8, Traverse du Syphon, F-13376 Marseille, France |