[1] Univ Roma Tor Vergata, Dipartimento Fis, Via Ric Sci 1, I-00133 Rome, Italy
[2] INAF OAR, Rome, Italy
[3] NRC, DAO HIA, Victoria, BC V9E 2E7, Canada
[4] IAC, E-38200 Tenerife, Spain
[5] INAF OACTe, I-64100 Teramo, Italy
[6] ESRIN, ASDC, ASI Sci Data Ctr, I-00044 Frascati, Italy
[7] Univ Bologna, Dipartimento Astron, I-40127 Bologna, Italy
[8] INAF OAB, I-40127 Bologna, Italy
[9] INAF OACN, I-80131 Naples, Italy
[10] Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy
[11] Univ Pisa, Dipartimento Fis, I-56127 Pisa, Italy
[12] GEPI, Observ Paris Meudon, F-75014 Paris, France
[13] INAF OAT, I-40131 Trieste, Italy
[14] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[15] Observ Cote Azur, F-06304 Nice, France