[1] Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China
[2] Chinese Acad Sci, South Amer Ctr Astron, Natl Astron Observ, Beijing 100101, Peoples R China
[3] Beijing Acad Sci & Technol, Beijing Planetarium, Beijing 100044, Peoples R China
[4] Chinese Acad Sci, Yunnan Observ, Kunming 650216, Peoples R China
[5] Chinese Acad Sci, Key Lab Struct & Evolut Celestial Objects, Kunming 650216, Peoples R China
[6] Int Ctr Supernovae, Yunnan Key Lab, Kunming 650216, Peoples R China
[7] Texas A&M Univ, Mitchell Inst Fundamental Phys & Astron, College Stn, TX 77843 USA