1. Institute of Astronomy, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UK
2. Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550 , F-67000 Strasbourg, France
3. Dipartimento di Fisica e Astronomia, Universitá degli Studi di Firenze , Via G. Sansone 1, I-50019 Sesto Fiorentino, Italy
4. INAF – Osservatorio Astrofisico di Arcetri , Largo E. Fermi 5, I-50125 Firenze, Italy
5. Department of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria, BC V8W 3P6, Canada
6. Instituto de Astrofísica de Canarias , E-38205 La Laguna, Tenerife, Spain
7. Departamento de Astrofísica, Universidad de La Laguna , E-38206 La Laguna, Tenerife, Spain
8. Max-Planck-Institut für Astronomie , Königstuhl 17, D-69117 Heidelberg, Germany
9. Kapteyn Astronomical Institute, University of Groningen , Postbus 800, NL-9700 AV Groningen, the Netherlands
10. Laboratoire d’astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire , CH-1290 Versoix, Switzerland
11. GEPI, Observatoire de Paris, Université PSL, CNRS , Place Jules Janssen, F-92195 Meudon, France