1. Finnish Centre for Astronomy with ESO (FINCA), Quantum, University of Turku, FI-20014, Finland
2. Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
3. Department of Physics, University of Warwick, Coventry CV4 7AL, UK
4. Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK
5. Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
6. Department of Astronomy, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA