1. INAF, Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, I-00133 Rome, Italy
2. Department of Astronomy, University of Maryland, College Park, MD 20742-4111, USA
3. Astrophysics Science Division, NASA Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, MD 20771, USA
4. Department of Physics and Astronomy, University of Nevada, 89154, Las Vegas, NV, USA
5. Joint Space-Science Institute, University of Maryland, College Park, Maryland 20742, USA
6. Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, UK
7. INAF-Istituto di Radioastronomia, Via Gobetti 101, I-40129, Bologna, Italy
8. CSIRO Astronomy and Space Science, PO Box 76, Epping, New South Wales 1710, Australia
9. Scuola Universitaria Superiore IUSS Pavia, Piazza della Vittoria 15, 27100 Pavia, Italy
10. INAF - IASF Milano, Via E. Bassini 15, I-20133 Milano, Italy
11. Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Via Bassi 6, I-27100 Pavia, Italy
12. School of Earth & Space Exploration, Arizona State University, AZ 85287, USA
13. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
14. INAF - OAS Bologna, Via P. Gobetti 93/3, I-40129 Bologna, Italy
15. Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara-shi Kanagawa 252-5258, Japan