1. Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
2. Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, the Netherlands
3. Argelander-Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn, Germany
4. Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia
5. Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
6. Australian Astronomical Observatory, PO Box 915, North Ryde, NSW 1670, Australia
7. INAF – Observatory of Capodimonte, Salita Moiariello, 16, I-800131 Naples, Italy
8. Kapteyn Astronomical Institute, University of Groningen, PO Box 800, NL-9700 AV Groningen, the Netherlands