Affiliation: | University of Hertfordshire, Department of Physical Sciences, Hatfield, Herts AL10 9AB;Isaac Newton Group of Telescopes, Apartado 321, E-38700 Santa Cruz de La Palma, Spain;Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA;School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS |