1. Purple Mountain Observatory, Chinese Academy of Sciences , Nanjing 210023, China
2. Mitchell Institute for Fundamental Physics and Astronomy, Texas A & M University , College Station, TX 77843, USA
3. Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University , Beijing 100084, China
4. Beijing Planetarium, Beijing Academy of Science and Technology , Beijing 100044, China
5. South America Center for Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, CAS , Beijing 100101, China
6. CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101, China