1. Departamento de Astronomía y Astrofísica, Universidad de Valencia, c/ Dr. Moliner, 50, E-46100 Burjassot (Valencia), Spain
2. Astronomy Unit, Department of Physics, University of Trieste, via Tiepolo 11, I-34131 Trieste, Italy
3. INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131 Trieste, Italy
4. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
5. INFN – National Institute for Nuclear Physics, Via Valerio 2, I-34127 Trieste, Italy
6. Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109, USA
7. Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica, I-00133 Roma, Italy
8. Instituto de Astronomía Teórica y Experimental (IATE), Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET), Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, X5000BGR Córdoba, Argentina
9. University Observatory Munich, Scheinerstr. 1, D-81679 Munich, Germany
10. Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Strasse 1, D-85748 Garching bei München, Germany
11. University of Southern California, Los Angeles, CA 90089, USA
12. Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA