[1] INAF, Osservatorio Astron, I-35122 Padua, Italy
[2] INAF, Osservatorio Astron Capodimonte, I-80131 Naples, Italy
[3] INAF, Osservatorio Astron, I-34131 Trieste, Italy
[4] Max Planck Inst Astrophys, D-85741 Garching, Germany
[5] Univ Barcelona, Dept Astron & Meteorol, E-08028 Barcelona, Spain
[6] Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2AZ, England
[7] European So Observ, D-85748 Garching, Germany
[8] Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia
[9] Stockholm Univ, SE-10691 Stockholm, Sweden