1. Shanghai Astronomical Observatory , Nandan Road 80, 200030 Shanghai , China
2. Tsung-Dao Lee Institute and Key Laboratory for Particle Physics, Astrophysics, and Cosmology, Ministry of Education, Shanghai Jiao Tong University , 200240 Shanghai , China
3. Department of Astronomy, School of Physics and Astronomy and Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai Jiao Tong University , 200240 Shanghai , China