1. Max Planck Institut für Astronomie, Königsthul 17, D-69117, Heidelberg, Germany
2. INAF Osservatorio Astrofisico e scienza dello Spazio di Bologna (OAS), Via Gobetti 93/3, I-40129 Bologna, Italy
3. Kapteyn Astronomical Institute, University of Groningen, NL-9747 AD Groningen, the Netherlands
4. Universität Stuttgart, Institut für Systemdynamik, Waldburgstr. 19, D-70563 Stuttgart, Germany
5. LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris Diderot, 5, place Jules Janssen, F-92190 Meudon, France