1. Department of Physics, The University of Hong Kong, Chong Yuet Ming Physics Building, Pokfulam Road, Hong Kong
2. Laboratory for Space Research, The University of Hong Kong, Block A, Cyberport 4, 100 Cyberport Road, Cyberport, Hong Kong
3. Institute for Astrophysics, University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna, Austria
4. Jodrell Bank Centre for Astrophysics, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
5. School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
6. Institute for Astronomy, KU Leuven, Celestijnenlaan 200D B2401, B-3001 Leuven, Belgium
7. Laboratoire Lagrange (UMR 7293), CNRS, Observatoire de la Cote d’Azur, Bd. de l’Observatoire, F-06304 Nice Cedex 4, France
8. Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia