[1] Chinese Acad Sci, Shanghai Astron Observ, Beijing, Peoples R China
[2] Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, Australia
[3] Univ Chinese Acad Sci, Beijing, Peoples R China
[4] Zhejiang Univ, Sch Phys, Hangzhou, Peoples R China
[5] Peking Univ, Kavli Inst Astron & Astrophys, Beijing, Peoples R China
[6] Peking Univ, Sch Phys, Dept Astron, Beijing, Peoples R China