[1] Washington Univ, Dept Phys, St Louis, MO 63130 USA
[2] Tanta Univ, Dept Phys, Tanta, Egypt
[3] Univ Leeds, Dept Phys, Leeds LS2 9JT, W Yorkshire, England
[4] Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA
[5] Iowa State Univ Sci & Technol, Dept Phys & Astron, Ames, IA 50011 USA
[6] Univ Calif Los Angeles, Dept Phys, Los Angeles, CA 90095 USA
[7] Gamma Ray Astrophys Grp Natl Space Sci, Huntsville, AL USA
[8] Ctr Technol, Huntsville, AL USA
[9] Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA
[10] Grinnell Coll, Dept Phys, Grinnell, IA 50112 USA
[11] Natl Univ Ireland Univ Coll Dublin, Dept Expt Phys, Dublin 4, Ireland
[12] Harvard Smithsonian Ctr Astrophys, Fred Lawrence Whipple Observ, Amado, AZ 85645 USA
[13] Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA
[14] Adler Planetarium, Dept Astron, Chicago, IL 60605 USA
[15] Astron Museum, Chicago, IL 60605 USA
[16] Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland
[17] Univ Utah, High Energy Astrophys Inst, Salt Lake City, UT 84112 USA
[18] Univ Arkansas, Dept Phys & Astron, Little Rock, AR 72204 USA
[19] McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada
[20] Depauw Univ, Dept Phys & Astron, Greencastle, IN 46135 USA
[21] Univ Maryland Baltimore Cty, Greenbelt, MD 20771 USA
[22] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[23] Mayo Inst Technol, Sch Sci, Galway, Ireland
[24] Cork Inst Technol, Dept Appl Phys & Instrumentat, Cork, Ireland