Affiliation: | Max-Planck-Institut fu¨r Astrophysik, Karl-Schwarzschild-Str. 1, D-85740 Garching bei Mu¨nchen, Germany,;National Council of Research (CNR-GNA),;Department of Astronomy, Padova University, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy |