[1] INAF Osservatorio Astrofis Arcetri, Largo Enr Fermi 5, I-50125 Florence, Italy
[2] Univ Firenze, Dipartimento Fis & Astron, Via Sansone 1, I-50019 Sesto Fiorentino, Firenze, Italy
[3] INAF IASF Palermo, Via Ugo Malfa 153, I-80146 Palermo, Italy
[4] Univ Modena & Reggio Emilia, Dept Phys Informat & Math, I-41125 Modena, Italy
[5] INAF IASF Milano, Via A Corti 12, I-20133 Milan, Italy
[6] Max Planck Inst Extraterr Phys, Giessenbachstr 1, D-85748 Garching, Germany
[7] Beijing Normal Univ, Inst Frontiers Astron & Astrophys, Beijing 102206, Peoples R China
[8] Univ Ferrara, Dipartimento Fis & Sci Terra, Via Saragat 1, I-44122 Ferrara, Italy
[9] Leiden Univ, Rapenburg 70, NL-2311 EZ Leiden, Netherlands
[10] Univ Groningen, Kapteyn Astron Inst, POB 800, NL-9700 AV Groningen, Netherlands
[11] Univ Padua, Dept Phys & Astron, Vicolo Osservatorio 3, I-35122 Padua, Italy
[12] INAF Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy