1. Lab for Computing and Applied Mathematics, National Institute for Space Research (INPE), S. J. dos Campos, 12245-970, Brazil
2. Astrophysics Division, National Institute for Space Research (INPE), S. J. dos Campos, 12245-970, Brazil
3. NIDTEC/FP-UNA, San Lorenzo, 2169-000, Paraguay
4. Departamento de Fisica, CCNE, Universidade Federal de Santa Maria, Santa Maria, 97105-900, Brazil
5. DCET, Universidade Estadual de Santa Cruz, Ilheus, 45662-900, Brazil