1. Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str 2, D-69120 Heidelberg, Germany
2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
3. School of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
4. Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands
5. Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, PL-00-716 Warsaw, Poland