1. Department of Astronomy, China West Normal University, Nanchong, Sichuan 637002, China
2. College of Physics and Information Science, Hunan Normal University, Changsha, Hunan 410081, China
3. Faculdade de Engenharia de Guaratinguetá, Universidade Estadual Paulista, 12516-410 Guaratinguetá, SP, Brazil
4. Instituto de Física e Química, Universidade Federal de Itajubá, 37500-903 Itajubá, MG, Brazil