1. School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
2. Department of Physics and Astronomy, Haverford College,370 Lancaster Avenue, Haverford, PA 19041, USA
3. Institute of Cosmology & Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX, UK
4. Department of Physics & Astronomy, University of Utah, Salt Lake City, UT 84112, USA
5. Centro de Astronomía, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1270300, Chile
6. Department of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260, USA
7. Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349, USA
8. McDonald Observatory, The University of Texas at Austin, 1 University Station, Austin, TX 78712, USA