1. Research Center for Astronomy and Applied Mathematics, Academy of Athens, Athens 11527, Greece
2. National Research Nuclear University (MEPhI), Moscow 115409, Russia
3. Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l université, F-67000 Strasbourg, France
4. Section of Astrophysics, Astronomy and Mechanics, Department of Physics, University of Athens, Athens 15783, Greece