[1] Univ Washington, Dept Astron, Seattle, WA 98195 USA
[2] Inst Adv Study, Princeton, NJ 08540 USA
[3] Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USA
[4] Princeton Univ Observ, Princeton, NJ 08544 USA
[5] Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA
[6] Max Planck Inst Extraterr Phys, D-85741 Garching, Germany
[7] Apache Point Observ, Sunspot, NM 88349 USA
[8] CALTECH, Dept Astron, Pasadena, CA 91125 USA
[9] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[10] Eotvos Lorand Univ, Dept Phys Complex Syst, H-1117 Budapest, Hungary
[11] Univ Tokyo, Sch Sci, Dept Astron, Tokyo 1810015, Japan
[12] Univ Tokyo, Sch Sci, Res Ctr Early Universe, Tokyo 1810015, Japan
[13] Univ Tokyo, Inst Cosm Ray Res, Tokyo 1888588, Japan
[14] USN Observ, Washington, DC 20392 USA
[15] Univ Chicago, Ctr Astron & Astrophys, Chicago, IL 60637 USA
[16] Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA
[17] Univ Sussex, Ctr Astron, Brighton BN1 9QJ, E Sussex, England
[18] Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA
[19] USN Observ, Flagstaff Stn, Flagstaff, AZ 86002 USA
[20] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15232 USA
[21] Astrophys Inst Potsdam, D-14482 Potsdam, Germany