Institution: | Astrophysics and Planetary Science Division, Department of Pure and Applied Physics, The Queen's University of Belfast, University Road, Belfast BT7 1NN; Department of Astronomy, University of Wisconsin, 5534 Sterling Hall, 475 North Charter Street, Madison, WI 53706, USA; Jodrell Bank Observatory, University of Manchester, near Macclesfield, Cheshire SK11 9DL |