1. Department of Physics and Astronomy , N283 ESC, Brigham Young University, Provo, UT 84602 , USA
2. Central (Pulkovo) Astronomical Observatory, Russian Academy of Sciences , Pulkovskoye Chaussee 65/1, St Petersburg 196140 , Russia
3. Saint Petersburg State University , Universitetskij pr. 28, St Petersburg 198504 , Russia
4. Special Astrophysical Observatory, Russian Academy of Sciences , Nizhnij Arkhyz 369167 , Russia
5. Department of Physics , 525 S Center St, Brigham Young University-Idaho, Rexburg, ID 83460 , USA