1. Department of Physics, Faculty of Science, Golestan University, Gorgan 49138-15739, Iran
2. Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha 55134-441, Iran
3. Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
4. Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen, Denmark
5. Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan