1. College of Material Science and Chemical Engineering, Hainan University, Hainan 570228, China
2. Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Ministry of Education, Nanjing 210093, China
3. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
4. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
5. University of Chinese Academy of Sciences, Beijing 100049, China
6. Department of Astronomy, Nanjing University, Nanjing 210093, China