[1] Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany
[2] Univ Cambridge, Inst Astron, Battcock Ctr Astrophys, Madingley Rd, Cambridge CB3 0HA, England
[3] Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, Germany
[4] Univ Manchester, Jodrell Bank, Ctr Astrophys, Sch Phys & Astron, Manchester M13 9PL, Lancs, England
[5] Netherlands Inst Radio Astron, ASTRON, Postbus 2, NL-7990 AA Dwingeloo, Netherlands
[6] Albert Einstein Inst, Max Planck Inst Gravitat Phys, Muhlenberg 1, D-14476 Golm, Germany
[7] INAF ORA Osservatorio Astron Cagliari, Via Sci 5, I-09047 Selargius, CA, Italy
[8] Univ Orleans, LPC2E, CNRS, F-45071 Orleans, France
[9] CNRS INSU, Stn Radioastron Nancay, Observ Paris, F-18330 Nancay, France
[10] Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England
[11] Univ Amsterdam, Astron Inst Anton Pannekoek, Sci Pk 904, NL-1098 XH Amsterdam, Netherlands
[12] Peking Univ, Kavli Inst Astron & Astrophys, Beijing 100871, Peoples R China
[13] CALTECH, TAPIR Theoret Astrophys, Pasadena, CA 91125 USA
[14] Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England
[15] Univ Paris 07, APC, UFR Phys, Batiment Condorcet, F-75205 Paris 13, France
[16] Swinburne Univ Technol, Ctr Astrophys & Supercomp, POB 218, Hawthorn, Vic 3122, Australia
[17] Albert Einstein Inst, Max Planck Inst Gravitat Phys, Callinstr 38, D-30167 Hannover, Germany
[18] CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA
[19] Univ Paris Diderot, Lab Univers & Theories, Observ Paris, CNRS INSU, 5 Pl Jules Janssen, F-92190 Meudon, France