1. Department of Physics, Kavli Institute for Astrophysics and Space Research, M.I.T., Cambridge, MA 02139, USA
2. Hereford Arizona Observatory, Hereford, AZ 85615, USA
3. Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
4. Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712, USA
5. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
6. Department of Physics and Astronomy, Trinity University, San Antonio, TX 78212-7200, USA
7. CRESST and X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
8. Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA