1. Institut für Physik und Astronomie, Universität Potsdam , Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam, Germany
2. Institute of Astronomy, Russian Academy of Sciences , 48 Pyatnitskaya St., Moscow, 119017, Russia
3. University of Vienna, Department of Astrophysics , Vienna, A-1180, Austria
4. School of Physics and Astronomy, University of Leicester , Leicester, LE1 7RH, UK
5. University of Exeter, Department of Physics and Astronomy , Exeter, Devon EX4 4QL, UK
6. Institute of Astronomy and Astrophysics , Academia Sinica, 11F of ASMAB, AS/NTU No.1, Section 4, Roosevelt Rd, Taipei 10617, Taiwan
7. Ural Federal University , 19 Mira Str., 620002 Ekaterinburg, Russia