Affiliation: | Department of Physics and Astronomy, University College London, London WC1E 6BT; Department of Physics and Astronomy, University of Leeds, Leeds LS2 9JT; Osservatario Astrofisico di Arcetri, Largo E.Fermi 5, I-50125 Firenze, Italy; Department of Physics, The Ohio State University, Columbus, OH 43210, USA |