1. Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
2. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
3. Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, P.R. China
4. Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, P.R. China
5. Centre for Astronomical Mega-Science, CAS, 20A Datun Road, Chaoyang District, Beijing 100012, P.R. China
6. School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA, UK
7. Max-Planck-Institut für Extraterrestrische Physik (MPE), Giessenbachstr, D-85748 Garching, Germany
8. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany
9. Purple Mountain Observatory, 2 West Beijing Road, Nanjing 230000, P.R. China
10. Department of Physics, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
11. Department of Astronomy, Cornell University, Space Sciences Building, Ithaca, NY 14853, USA
12. Department of Physics, Centre for Extragalactic Astronomy, Durham University, South Road, Durham DH1 3LE, UK
13. European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago, Chile
14. Institut d’Astrophysique de Paris, Sorbonne Université, CNRS,UMR 7095, 98 bis bd Arago, F-75014 Paris, France
15. Department of Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, UK
16. Sterrewacht Leiden, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands