[1] Observ Astron, RA-5000 Cordoba, Argentina
[2] Consejo Nacl Invest Cient & Tecn, RA-1033 Buenos Aires, DF, Argentina
[3] Observ Midi Pyrenees, CNRS, UMR 5572, F-31400 Toulouse, France
[4] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA
[5] European So Observ, D-85748 Garching, Germany
[6] Observ Nacl, BR-20921400 Rio De Janeiro, Brazil
[7] Dartmouth Coll, Dept Phys & Astron, Hanover, NH 03755 USA
[8] Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95064 USA
[9] UFRJ, Observ Valongo, BR-20080090 Rio De Janeiro, Brazil