[1] Hokkaido Univ, Grad Sch Sci, Dept Cosmosci, Sapporo, Hokkaido 0600810, Japan
[2] NASA, Goddard Space Flight Ctr, Lab Astron & Solar Phys, Greenbelt, MD 20771 USA
[3] Univ Tokyo, Sch Sci, Dept Astron, Tokyo 113, Japan
[4] Max Planck Inst Astrophys, D-85741 Garching, Germany
[5] Univ Tokyo, Sch Sci, Res Ctr Early Univ, Tokyo 113, Japan