[1] Max Planck Inst Grav Phys, Albert Einstein Inst, D-30167 Hannover, Germany
[2] Leibniz Univ Hannover, D-30167 Hannover, Germany
[3] Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany
[4] Natl Radio Astron Observ, 520 Edgemont Rd, Charlottesville, VA 22903 USA
[5] INAF Osservatorio Astron Cagliari, Via Sci 5, I-09047 Selargius, CA, Italy
[6] West Virginia Univ, Dept Phys & Astron, POB 6315, Morgantown, WV 26506 USA
[7] West Virginia Univ, Ctr Gravitat Waves & Cosmol, Chestnut Ridge Res Bldg, Morgantown, WV 26505 USA
[8] SETI Inst, 339 Bernardo Ave,Suite 200, Mountain View, CA 94043 USA
[9] Swinburne Univ Technol, Ctr Astrophys & Supercomp, POB 218, Hawthorn, Vic 3122, Australia
[10] South African Radio Astron Observ, 2 Fir St,Black River Pk, ZA-7925 Observatory, South Africa
[11] George Mason Univ, Fairfax, VA 22030 USA
[12] Univ Cape Town, Dept Math & Appl Math, High Energy Phys Cosmol & Astrophys Theory HEPCAT, ZA-7701 Rondebosch, South Africa
[13] Univ Amsterdam, Anton Pannekoek Inst Astron, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands
[14] Netherlands Inst Radio Astron, ASTRON, Oude Hoogeveensedijk 4, NL-7991 PD Dwingeloo, Netherlands
[15] Univ Manchester, Jodrell Bank Ctr Astrophys, Dept Phys & Astron, Manchester M13 9PL, England
[16] Univ British Columbia, Dept Phys & Astron, 6224 Agr Rd, Vancouver, BC V6T 1Z1, Canada
[17] Chinese Acad Sci, Natl Astron Observ, A20 Datun Rd, Beijing 100101, Peoples R China