SCYON Abstract

Received on December 6 2000

The geometry of the star motions in the nucleus region of the Ursa Major kinematic group

Authors	N.V. Chupina, V.G. Reva, S.V. Vereshchagin
Affiliation	Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya Str., 109017 Moscow, Russia
Submitted to	Will be submitted to Astron. Astrophys Suppl.
Contact	svv@inasan.rssi.ru
URL	http://www.inasan.rssi.ru/~svv/
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Abstract

The structure of central part of the UMa star kinematic group was considered according to the data from Hipparcos, Tycho and ACT catalogues. We have shown that there are a few subsystems of stars. The first include eight stars very compactly located on the proper motion diagram and have the normal proper motion distribution.The status of the second group considered early as belonging to the nucleus is undeterminate for two reasons: it much differ kinematically and some stars have large errors of astrometric parameters. The last third group include six field stars. The question about their joint existence in common region of space remains open. The well-known Mizar and Alcor have apperead in the different subsystems and do not belong to the united star system. The published radial velocities are determined as a rule with unsufficient accuracy in compare with the errors of available now proper motions. The high precision of radial velocities measurements is needed to the deep study of the star kinematic inside UMa star system.