[1] Taras Shevchenko Natl Univ Kyiv, Astron Observ, UA-01033 Kiev, Ukraine
[2] Natl Tech Univ Ukraine, Igor Sikorsky Kyiv Polytech Inst, UA-03056 Kiev, Ukraine
[3] Univ Catania, Osseravatorio Astrofis Catania, INAF, I-95123 Catania, Italy
[4] Russian Acad Sci, Inst Astron, Moscow 119017, Russia