[1] UCL, Dept Phys & Astron, Gower St, London WC1E 6BT, England
[2] INAF Osservatorio Astron Roma, Via Frascati 33, I-00078 Monte Porzio Catone, Italy
[3] Univ Andres Bello, Dept Ciencias Fis, Fernandez Concha 700, Santiago, Chile
[4] Univ Geneva, Dept Astron, Observ Geneve, 51 Chemin Pegasi, CH-1290 Versoix, Switzerland
[5] IRAP, CNRS, 14 Ave E Belin, F-31400 Toulouse, France
[6] INAF Osservatorio Astron Bologna, Via P Gobetti 93-3, I-40129 Bologna, Italy
[7] Univ La Serena, Inst Invest Multidisciplinar Ciencia & Tecnol, La Serena 1305, Chile
[8] Univ La Serena, Dept Fis & Astron, Av Juan Cisternas 1200 Norte, La Serena, Chile
[9] INAF Osservatorio Astrofis & Sci Spazio Bologna, Via Piero Gobetti 93-3, I-40129 Bologna, Italy
[10] INAF Astron Observ Trieste, Via GB Tiepolo 11, I-34143 Trieste, Italy
[11] IFPU Inst Fundamental Phys Universe, Via Beirut 2, I-34151 Trieste, Italy
[12] Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA
[13] European Southern Observ ESO, Alonso de Cordova 3107, Santiago 19001, Chile
[14] INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy
[15] Univ Bologna, Dept Phys & Astron Augusto Righi DIFA, Via Gobetti 93-2, I-40129 Bologna, Italy