1. Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova, Vicolo dell’Osservatorio 3, I-35122 Padova, Italy
2. Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, A-1180 Wien, Austria
3. Osservatorio Astronomico di Padova – INAF, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
4. Aix Marseille Univ., CNRS, CNES, LAM, 38, rue Frédéric Joliot-Curie 13388 Marseille, France