Institution: | Department of Physics, University of Durham, Durham DH1 3LE;Astrophysics, Department of Physics, Keble Road, Oxford OX1 3LE;Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, the Netherlands;Instituto de Astronomia, UNAM, Ap. 70-264, 04510 Mexico, DF, Mexico |