1. Max-Planck-Institut für extraterrestrische Physik , Gießenbachstraße 1, D-85748 Garching, Germany
2. Kavli Institute for Particle Astrophysics and Cosmology, Stanford University , 452 Lomita Mall, Stanford, CA 94305-4085, USA
3. Institute of Astronomy , Madingley Road, Cambridge CB3 0HA, UK
4. INAF–IASF Palermo , Via U. La Malfa 153, I-90146 Palermo, Italy
5. School of Physics & Astronomy, University of Nottingham , University Park, Nottingham NG7 2RD, UK
6. Institute of Space and Astronautical Science (ISAS) , Japan Aerospace Exploration Agency (JAXA), Kanagawa 252-5210, Japan
7. Astrophysics Science Division, X-ray Astrophysics Laboratory , NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
8. Department of Physics and Astronomy, University of Alabama in Huntsville , Huntsville, AL 35899, USA
9. Harvard–Smithsonian Center for Astrophysics , 60 Garden Street, Cambridge, MA 02138, USA