1. Department of Astronomy, University of Maryland, College Park, MD 20742, USA
2. Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA
3. Space Telescope Science Institute, Baltimore, MD 21218, USA
4. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA
5. X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
6. Department of Physics, University of Sydney, Sydney, NSW 2006, Australia
7. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
8. Department of Physics, University of California, Santa Barbara, CA 93106, USA
9. Max Planck Institute for Extraterrestrial Physics (MPE), D-85748 Garching, Germany
10. Department of Physics, Rhodes College, Memphis, TN 38112, USA
11. Universities Space Research Association, 7178 Columbia Gateway Drive, Columbia, MD 21046, USA
12. Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA