1. School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China
2. Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Nanjing 210093, China
3. Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, AP 70-264, 04510 Mexico, DF, Mexico
4. Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK
5. Instituto de Física, Universidade Federal do Rio Grande do Sul, Campus do Vale, 91501-970 Porto Alegre, Brasil
6. Departamento de Física, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
7. Laboratório Interinstitucional de e-Astronomia, 77 Rua General José Cristino, 20921-400 Rio de Janeiro, Brasil
8. European Southern Observatory, D-85748 Garching, Germany
9. Apache Point Observatory and New Mexico State University, PO Box 59, Sunspot, NM 88349-0059, USA
10. Sternberg Astronomical Institute, Moscow State University, 119991 Moscow, Russia
11. Special Astrophysical Observatory of the Russian AS, 369167 Nizhnij Arkhyz, Russia
12. McDonald Observatory, The University of Texas at Austin, 1 University Station, Austin, TX 78712, USA