Institution: | Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ;Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA;Laboratory for High Energy Astrophysics, NASA/Goddard Space Flight Center, Code 660, Greenbelt, MD 20771, USA;Department of Physics &Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA |