1. School of Physics and Astronomy, University of Minnesota , Minneapolis, Minnesota 55455 , USA
2. Department of Physics and Astronomy, University of Minnesota – Duluth , Duluth, Minnesota 55812 , USA
3. Joint Space-Science Institute, University of Maryland , College Park, MD 20742 , USA
4. Astrophysics Science Division, NASA Goddard Space Flight Center , MC 661, Greenbelt, MD 20771 , USA
5. Department of Astronomy, University of Maryland , College Park, MD 20742 , USA
6. Institute of Physics and Astronomy, Theoretical Astrophysics, University Potsdam , Haus 28, Karl-Liebknecht-Str. 24/25, D-14476, Potsdam , Germany
7. Max Planck Institute for Gravitational Physics (Albert Einstein Institute) , Am Mühlenberg 1, Potsdam D-14476 , Germany
8. IPAC, California Institute of Technology , 1200 E. California Blvd, Pasadena, CA 91125 , USA
9. Division of Physics, Mathematics, and Astronomy, California Institute of Technology , Pasadena, CA 91125 , USA
10. Nikhef – National Institute for Subatomic Physics, Science Park , NL-1098 XG Amsterdam, the Netherlands
11. Institute for Gravitational and Subatomic Physics (GRASP), Utrecht University , Princetonplein 1, NL-3584 CC Utrecht , the Netherlands
12. Caltech Optical Observatories, California Institute of Technology , Pasadena, CA 91125 , USA