Affiliation: | Institute of Applied Physics of the Russian Academy of Sciences, Ulyanova 46, 603950 Nizhny Novgorod, Russia;Nizhny Novgorod University, Gagarin av. 23, 603950 Nizhny Novgorod, Russia;Helsinki University Observatory, University of Helsinki, Tähtitorninmäki, PO Box 14, FIN-00014 Helsinki, Finland;School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT |