[1] Stockholm Univ, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden
[2] Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA
[3] Univ Toronto, Toronto, ON M1C 1A4, Canada
[4] Univ Observ Munich, D-81679 Munich, Germany
[5] Nicolaus Copernicus Astron Ctr, PL-00716 Warsaw, Poland
[6] Queen Mary Univ London, Astron Unit, London E1 4NS, England
[7] Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England
[8] Inst Astron & Astrophys, D-72076 Tubingen, Germany
[9] Univ Cambridge, DAMTP, Ctr Math Sci, Cambridge CB3 0WA, England
[10] Max Planck Inst Astron, D-69117 Heidelberg, Germany
[11] Uppsala Astron Observ, Dept Space Phys & Astron, S-75120 Uppsala, Sweden
[12] Univ Paris 07, AIM, CEA, CNRS,UMR 7158,Serv Astrophys, F-91191 Gif Sur Yvette, France
[13] Univ Nacl Autonoma Mexico, IA, Mexico City 04510, DF, Mexico
[14] Leiden Observ, NL-2300 RA Leiden, Netherlands
[15] Observ Paris, Luth, F-92195 Meudon, France
[16] Univ Chicago, ASC FLASH Ctr, Chicago, IL 60637 USA
[17] Univ Edinburgh, Astron Inst, Scottish Univ Phys Alliance, Edinburgh EH9 3HJ, Midlothian, Scotland