1. Department of Physics, University of California, Santa Barbara, CA 93106, USA
2. Department of Astronomy, University of Maryland, College Park, MD 20742, USA
3. Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA
4. Space Telescope Science Institute, Baltimore, MD 21218, USA
5. Max-Planck-Institute for Extraterrestrial Physics (MPE), D-85748 Garching, Germany
6. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA
7. Department of Physics, University of Sydney, Sydney, NSW 2006, Australia
8. Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA