1. Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023, China
2. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
3. Department of Astronomy, Beijing Normal University, Beijing 100875, China
4. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
5. Department of Astronomy, Yunnan University, Kunming 650091, China