1. Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS) , Av. Bento Goncalves, 9500 Porto Alegre, RS, Brazil
2. Instituto de Astrofísica de Canarias , Calle Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain
3. Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP , Rua das Estrelas, P-T4150-762 Porto, Portugal
4. Centre for Astrophysics Research, University of Hertfordshire , College Lane, Hatfield AL10 9AB, UK
5. Shanghai Astronomical Observatory, Chinese Academy of Sciences , 80 Nandan Rd., Shanghai 200030, China
6. School of Mathematics and Computer Science, Yunnan Minzu University , 2929 Yuehua Street, Kunming 650500, China