[1] Dartmouth Coll, Dept Phys & Astron, Wilder Lab 6127, Hanover, NH 03755 USA
[2] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA
[3] Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95064 USA
[4] Observ Valongo, BR-20080090 Rio De Janeiro, Brazil
[5] Observ Nacl, BR-20921400 Rio De Janeiro, Brazil
[6] European So Observ, D-85748 Garching, Germany
[7] Observ Astron, RA-5000 Cordoba, Argentina
[8] Consejo Nacl Invest Cient & Tecn, RA-1033 Buenos Aires, DF, Argentina
[9] Observ Midi Pyrenees, Astrophys Lab, F-31400 Toulouse, France