P. A. B. Galli, R. Teixeira, C. Ducourant, C. Bertout, P. Benevides-Soares
Context: Convergent point (CP) search methods are important tools for
studying the kinematic properties of open clusters and young associations whose
members share the same spatial motion.
Aims: We present a new CP search strategy based on proper motion data. We
test the new algorithm on synthetic data and compare it with previous versions
of the CP search method. As an illustration and validation of the new method we
also present an application to the Hyades open cluster and a comparison with
independent results.
Methods: The new algorithm rests on the idea of representing the stellar
proper motions by great circles over the celestial sphere and visualizing their
intersections as the CP of the moving group. The new strategy combines a
maximum-likelihood analysis for simultaneously determining the CP and selecting
the most likely group members and a minimization procedure that returns a
refined CP position and its uncertainties. The method allows one to correct for
internal motions within the group and takes into account that the stars in the
group lie at different distances.
Results: Based on Monte Carlo simulations, we find that the new CP search
method in many cases returns a more precise solution than its previous
versions. The new method is able to find and eliminate more field stars in the
sample and is not biased towards distant stars. The CP solution for the Hyades
open cluster is in excellent agreement with previous determinations.
View original:
http://arxiv.org/abs/1112.3542
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