[1] Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95064 USA
[2] Univ Penn, Dept Phys & Astron, Philadelphia, PA 19104 USA
[3] Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA
[4] Natl Opt Astron Observ, Tucson, AZ 85719 USA
[5] Columbia Univ, Astrophys Lab, New York, NY 10027 USA
[6] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
[7] Bell Labs, Lucent Technol, Murray Hill, NJ 07974 USA
[8] Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 USA
[9] Pontificia Univ Catolica Chile, Dept Astron & Astrofis, Santiago 22, Chile
[10] Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia
[11] Univ Calif San Diego, Dept Phys, La Jolla, CA 92093 USA
[12] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA
[13] Max Planck Inst Astrophys, D-85748 Garching, Germany
[14] Univ Washington, Dept Astron, Seattle, WA 98195 USA
[15] Univ Washington, Dept Phys, Seattle, WA 98195 USA
[16] European So Observ, D-85748 Garching, Germany
[17] Univ Oxford, Oxford OX1 3RH, England
[18] McMaster Univ, Dept Phys & Astron, Hamilton, ON L8S 4M1, Canada