[1] Max Planck Inst Extraterr Phys, D-85748 Garching, Germany
[2] Osservatorio Astron Bologna, INAF, I-40127 Bologna, Italy
[3] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA
[4] Osserv Astron Roma, INAF, I-00044 Monte Porzio Catone, Italy
[5] Univ Padua, Dipartimento Astron, I-35122 Padua, Italy
[6] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA
[7] European So Observ, D-85748 Garching, Germany
[8] Univ Roma Tre, Dipartimento Fis, I-00146 Rome, Italy
[9] Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy
[10] CNR, INAF, IASF, Sez Milano, I-20133 Milan, Italy
[11] INTEGRAL, Sci Data Ctr, CH-1290 Versoix, Switzerland
[12] Univ Hawaii, Astron Inst, Honolulu, HI 96822 USA
[13] CALTECH, Pasadena, CA 91125 USA
[14] Astrophys Lab, F-13376 Marseille 12, France
[15] Yale Univ, Dept Astron, New Haven, CT 06520 USA
[16] INAF, IRA, I-40129 Bologna, Italy