1. Department of Astronomy and Astrophysics, The University of Chicago , Chicago, IL 60637, USA
2. The Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USA
3. Department of Astronomy, University of Michigan , Ann Arbor, MI 48109, USA
4. Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden, the Netherlands
5. Department of Astronomy, University of Maryland , College Park, MD 20742, USA
6. X-ray Astrophysics Laboratory , NASA/GSFC, Greenbelt, MD 20771, USA
7. Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA
8. Department of Physics and Astronomy, University of Hawai’i at Hilo , Hilo, HI 96720, USA
9. Department of Physics, University of Milan Bicocca , Piazza della Scienza 3, I-20126 Milano, Italy