[1] Univ Calif Davis, Dept Phys, Davis, CA 95616 USA
[2] Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA
[3] Space Telescope Sci Inst, Baltimore, MD 21218 USA
[4] Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA
[5] Natl Opt Astron Observ, Tucson, AZ 85726 USA