Clusterix 2.0. A Virtual Observatory tool to estimate cluster membership
  probability
  Clusterix 2.0 is a web-based, Virtual Observatory-compliant, interactive tool
for the determination of membership probabilities in stellar clusters based on
proper motion data using a fully non-parametric method. In the area occupied by
the cluster, the frequency function is made up of two contributions: cluster
and field stars. The tool performs an empirical determination of the frequency
functions from the Vector-Point Diagram without relying in any previous
assumption about their profiles. Clusterix 2.0 allows to search in an
interactive way the appropriate spatial areas until an optimal separation of
the two populations is obtained. Several parameters can be adjusted to make the
calculation computationally feasible without interfering in the quality of the
results. The system offers the possibility to query different catalogues, such
as Gaia, or upload the user own data. The results of the membership
determination can be sent via SAMP to VO tools like TopCat.
  We apply Clusterix 2.0 to several open clusters with different properties and
environments to show the capabilities of the tool: an area of five degrees
around NGC 2682 (M 67), an old, well known cluster; a young cluster NGC 2516
with a striking elongate structure extended up to four degrees; NGC 1750 & NGC
1758, a pair of partly overlapping clusters; in the area of NGC 1817 we confirm
a little-known cluster, Juchert 23; and in an area with many clusters we
disentangle the existence of two overlapping clusters where only one was
previously known: Ruprecht 26 and the new, Clusterix 1.
