1. Department of Physics, Yunnan Normal University, Kunming 650092, China
2. Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, China
3. Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Shandong University, Weihai, 264209
4. Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China
5. Department of Physics and Astronomy, Sun Yat-Sen University, Zhuhai 519082, China