1. INAF Osservatorio Astronomico di Roma, Frascati Str. 33, 00078 Monte Porzio Catone, Italy
2. Astronomical Observatory, Taras Shevchenko National University of Kyiv, Observatorna Str. 3 Kyiv, 04053 Kiev, Ukraine
3. Dipartimento di Fisica e Astronomia, University of Catania, Viale Andrea Doria 6, 95125 Catania, Italy
4. Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya Str., 48, 119017 Moscow, Russia