[1] Department of Physics and Astronomy, Queen's University of Belfast, BT7 INN, Northern Ireland, United Kingdom
[2] UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, United Kingdom
[3] Isaac Newton Group of Telescopes, Apartado de Correos 321, Canary Islands, Spain
[4] Institute de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
[5] Steward Observatory, University of Arizona, Tucson, AZ 85712, United States
[6] Department of Astronomy, University of Maryland, College Park, MD 20742, United States