1. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122, Australia
2. Universitäts-Sternwarte München, Scheinerstraße 1, D-81679 München, Germany
3. Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, Giessenbachstr., D-85741 Garching, Germany
4. Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan
5. Sterrewacht Leiden, Leiden University, Niels-Bohr-Weg 2, NL-2300 CA Leiden, the Netherlands