1. National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China.
2. Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China.
3. Department of Astronomy, Peking University, Beijing 100871, China.
4. Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China.
5. University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049, China.
6. Department of Astronomy, Beijing Normal University, Beijing 100875, China.
7. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
8. Nevada Center for Astrophysics, University of Nevada, Las Vegas, NV 89154, USA.
9. Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA.
10. Zhejiang Lab, Hangzhou, Zhejiang 311121, China.
11. Faculty of Engineering and Natural Sciences, Sabancı University, 34956 İstanbul, Turkey.
12. Department of Physics, The George Washington University, 725 21st St. NW, Washington, DC 20052, USA.
13. Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany.
14. GuangXi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, GuangXi University, Naning 530004, China.
15. South-Western Institute for Astronomy Research, Yunnan University, Kunming 650500, Yunnan, China.
16. Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai 200030, China.