1. Department of Physics, School of Sciences, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran
2. Research Institute for Astronomy and Astrophysics of Maragha (RIAAM)- Maragha, P. O. Box: 55134 - 441, Iran
3. Department of Astronomy, Xiamen University, Xiamen, Fujian 361005, China