1. INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, I-40129 Bologna, Italy
2. Research School of Astronomy and Astrophysics – The Australian National University, Canberra ACT 2611, Australia
3. INAF-Osservatorio Astronomico di Torino, Via Osservatorio 30, I-10025 Pino Torinese, Italy
4. INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
5. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany
6. Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife, Spain
7. Universidad de La Laguna, Dpto. Astrofisica, E-38206 La Laguna, Tenerife, Spain
8. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, NL-9700 AV Groningen, the Netherlands
9. Dipartimento di Fisica and Astronomia, Università degli Studi di Bologna, Viale Berti Pichat, 6/2, I-40127 Bologna, Italy
10. Leiden Observatory, Leiden University, Postbus 9513, NL-2300 RA Leiden, the Netherlands
11. Max Planck Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany
12. Université de Strasbourg, CNRS, UMR 7550, F-67000 Strasbourg, France
13. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
14. INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio, Italy
15. Space Telescope Science Institute, Baltimore, MD 21218, USA