Cool Stars 14 - Submitted Abstract # 12
This version created on 05 October 2006

Characterisation of the Ursa Major group


Matthias Ammler, AIU Jena
Eike Guenther, TLS Tautenburg
Brigitte Koenig, University of Pittsburgh

The young Ursa Major (UMa) group (200-600  Myrs) is comprised of the
stars in the UMa cluster in the Big Dipper constellation and of many
co-moving stars spread over the whole sky.  In order to assign a star
as a member of a moving group, not only kinematic criteria have to be
taken into account but also spectroscopically determined parameters.
In here we present a study to known members of the UMa moving group,
which aims in better assigning criteria of the membership.  19 out of
56 kinematic Ursa Major (UMa) group members can be analysed following
the method of Fuhrmann (2004).  We extend the work of Fuhrmann (2004)
on the UMa group beyond 25 pc and add analyses of 10  stars.  Hence
stellar parameters of by now 16 mid- and late-type kinematic UMa group
members are inferred homogeneously.  We calculated spectroscopic
distances which agree well with the Hipparcos distances confirming the
accuracy of the derived stellar parameters.  Our results indicate an
iron mean abundance of [Fe/H]=-0.03 which is by about 0.06 dex higher
than previous measurements.  Furthermore we analysed the equivalent
widths of the Li I 6707.8 AA doublet of in total 20  kinematic UMa
group members and detect some indications that the large age spread of
the UMa group may be not intrinsic.  We propose to use iron abundance
and lithium equivalent widths with kinematic membership criteria in
order to decide on the UMa group membership of further candidates.

----------------------------------