1. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
2. Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China
3. Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Sternwartstr. 7, D-96049 Bamberg, Germany
4. Department of Astronomy and Physics, Saint Mary’s University, 923 Robie Street, Halifax, NS B3H 3C 3, Canada
5. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
6. Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA
7. European Space Agency (ESA), European Space Astronomy Centre (ESAC), E-28691 Villanueva de la Cañada, Spain
8. Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450, USA