1. Jeremiah Horrocks Institute, School of Physical Sciences and Computing, University of Central Lancashire, Preston PR1 2HE, UK
2. Instituto de Astronomia, Geofísica e Ciêcias Atmosféricas, Univ. de São Paulo, Rua do Matão 1226, 05508-090 São Paulo, Brazil
3. Instituto de Astrofísica de Canarias, Vía Láctea, E-38205 La Laguna, Tenerife, Spain
4. Universidad de La Laguna, Departamento de Astrofísica, E-38206 La Laguna, Tenerife, Spain
5. Department of Astronomy, Harvard University, Cambridge, MA 02138, USA