Key Laboratory of Optical Astronomy;
National Astronomical Observatories;
Chinese Academy of Sciences;
Beijing 100012;
China;
Department of Astronomy;
Beijing Normal University;
Beijing 100875;
China;
Institute of Space Science and Physics;
Shandong University at Weihai;
Weihai 264209;
China;
Shandong Provincial Key Laboratory of Optical Astronomy & Solar-Terrestrial Environment;
Weihai 264209;
China;
Max Planck Institute for Astronomy;
K6nigstuhl 17;
69117 Heidelberg;
Germany;