1. Department of Physics and Joint Institute for Nuclear Astrophysics, Western Michigan University, Kalamazoo, Michigan, USA.
2. National Astronomical Observatory of Japan, Tokyo, Japan.
3. Department of Physics, Department of Astronomy, The Ohio State University, Columbus, Ohio, USA.
4. Department of Astronomy, Graduate School of Science, University of Tokyo, Tokyo, Japan.
5. School of Physics and Nuclear Energy Engineering, Beihang University (Beijing University of Aeronautics and Astronautics), Beijing, P.R. China.