Institution: | Astronomy Group, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB;University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL;Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, the Netherlands;Astronomy Group, University College London, London WC1E 6BT |