1. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Datun Road 20A, Beijing, 100012, China
2. Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany
3. Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München, Germany
4. National Astronomical Observatories Nanjing Institute of Astronomical Optics & Technology, Chinese Academy of Sciences, Nanjing, Jiangsu 210042, China
5. Key Laboratory of Astronomical Optics & Technology, Chinese Academy of Sciences, Nanjing, Jiangsu 210042, China