1. National Astronomical Observatories, Chinese Academy of Sciences , 20A Datun Road, Chaoyang District, Beijing 100101 , China
2. Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206 , China
3. Max-Planck Institut für Radioastronomie , Auf dem Hügel 69, D-53121 Bonn , Germany
4. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester , Manchester M13 9PL , UK
5. Kavli Institute for Astronomy and Astrophysics, Peking University , Beijing 100871 , China
6. School of Astronomy and Space Science, University of Chinese Academy of Sciences , Beijing 100049 , China
7. Department of Physics and Astronomy, West Virginia University , PO Box 6315, Morgantown, WV 26506 , USA
8. Center for Gravitational Waves and Cosmology, West Virginia University , Chestnut Ridge Research Building, Morgantown, WV 26505 , USA
9. Department of Physics, McGill University , 3600 rue University, Montréal, QC H3A 2T8 , Canada
10. McGill Space Institute, McGill University , 3550 rue University, Montréal, QC H3A 2A7 , Canada
11. Xinjiang Astronomical Observatory, Chinese Academy of Sciences , Urumqi, Xinjiang 830011 , People’s Republic of China