1. Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
2. TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA
3. The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101, USA
4. Department of Physics, University of California, Davis, CA 95616, USA
5. Department of Physics and Astronomy and CIERA, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
6. Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA
7. Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA