[1] INAF, Osservatorio Astrofisico di Torino, via Osservatorio 20, Pino Torinese,10025, Italy
[2] Instituto de Astrofísica de Canarias, C/Via Láctea S/N, La Laguna,Tenerife,38200, Spain
[3] Departamento de Astrofísica, Universidad de La Laguna, La Laguna,Tenerife,38205, Spain
[4] INAF, Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, Padova,35122, Italy
[5] Dip. di Fisica e Astronomia Galileo Galilei, Università di Padova, Vicolo dell'Osservatorio 2, Padova,35122, Italy
[6] Harvard-Smithsonian Center for Astrophysics, Cambridge,MA,02138, United States
[7] INAF, Osservatorio Astrofisico di Catania, via S.Sofia 78, Catania,95123, Italy
[8] INAF, Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, Napoli,80131, Italy
[9] Dipartimento di Fisica, Universitá di Torino, via P. Giuria 1, Torino,10125, Italy
[10] Landessternwarte Königstuhl, Zentrum für Astronomie, Universität Heidelberg, Königstuhl 12, Heidelberg,69117, Germany
[11] INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, Merate,LC,23807, Italy
[12] Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton,NJ,08544, United States
[13] Department of Physics and Astronomy, Vanderbilt University, Nashville,TN,37235, United States
[14] Department of Physics and Astronomy, University of Louisville, Louisville,KY,40292, United States
[15] Fundación Galileo Galilei, INAF, Rambla José Ana Fernandez Pérez 7, Breña Baja,TF,38712, Spain
[16] INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, Palermo,90134, Italy
[17] INAF, IASF Milano, via Bassini 15, Milano,20133, Italy
[18] INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, Trieste,34143, Italy
[19] Universidad de Atacama, Departamento de Fisica, Copayapu 485, Copiapo, Chile
[20] Max Planck Institute for Astronomy, Königstuhl 17, Heidelberg,69117, Germany
[21] Astrophysics Group, Keele University, Staffordshire,ST5 5BG, United Kingdom