1. Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
2. Department of Physics, North-West University, Mafikeng Campus, Private Bag X2046, Mmabatho 2745, South Africa
3. Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, Porto PT4150-762, Portugal
4. Department of Astronomy, The University of Tokyo, Tokyo 113-0033, Japan
5. Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, Leuven B-3001, Belgium