1. Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife, Spain
2. Departamento de Astrofísica, Universidad de La Laguna (ULL), E-38206 La Laguna, Tenerife, Spain
3. Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611, USA
4. Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden
5. Tuorla Observatory, University of Turku, Väisäläntie 20, FI-21500 Piikkiö, Finland
6. Department of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK