1. Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206 , China
2. Department of Astronomy, Beijing Normal University , Beijing 100875 , China
3. Shanghai Astronomical Observatory, Chinese Academy of Sciences , Nandan Road 80, Shanghai 200030 , China
4. Department of Astronomy, School of Physics and Technology, Wuhan University , Wuhan 430072 , China
5. CAS Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101 , China