[1] Observ Astron, F-67000 Strasbourg, France
[2] Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia
[3] Macquarie Univ, Dept Phys & Astron, N Ryde, NSW 2109, Australia
[4] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[5] NRC Herzberg Inst Astrophys, Victoria, BC V9E 2E7, Canada
[6] Dalhousie Univ, Dept Phys & Atmospher Sci, Halifax, NS B3H 4R2, Canada
[7] Max Planck Inst Astron, D-69117 Heidelberg, Germany
[8] Univ Massachusetts, Dept Astron, Amherst, MA 01003 USA
[9] Univ Edinburgh, Inst Astron, Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland
[10] Lyce Int Pontonniers, F-67000 Strasbourg, France
[11] Australian Natl Univ, Mt Stromlo Observ, Weston, ACT 2611, Australia
[12] Univ Victoria, Dept Phys & Astron, Victoria, BC V8P 5C2, Canada
[13] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA
[14] Observ Paris, LERMA, CNRS, UMR 8112, F-75014 Paris, France
[15] Queens Univ, Dept Phys Engn Phys & Astron, Kingston, ON K7L 3N6, Canada