1. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
2. Tianjin Astrophysics Center, Tianjin Normal University, Tianjin 300387, China
3. School of Physics, University of New South Wales, NSW 2052, Australia
4. Nanjing Institute of Astronomical Optics and Technology, Nanjing 210042, China
5. Purple Mountain Observatory, Nanjing 210008, China