摘要：Aims. One of the results of the Milky Way Star Clusters (MWSC) survey
was the detection of a slight under-density of old (ca. 1 Gyr) clusters within the nearest
kilo-parsec from the Sun. This under-density may be due to an ineffectiveness in the
detection of larger structures with lower surface brightness. We report on our attempts to
reveal such clusters.
Methods. We derived proper motions from a combination of Tycho-2 with
URAT1, and obtained a mean precision of about 1.4 mas/yr per co-ordinate for 1.3 million
stars north of −20° declination. We cut the sky into narrow proper motion
slices and searched for spatial over-densities of stars in each slice. We then examined
stars from over-densities in optical and near-infrared colour-magnitude diagrams to
determine if they are compatible with isochrones of a cluster. We estimated the field star
contamination using our data and the Besançon Galactic model.
Results. We detected nine hitherto unknown open clusters in the vicinity
of the Sun with ages between 70 Myr and 1 Gyr, and distances between 200 and 500 pc.
关键词：open clusters and associations: general;catalogs;surveys;proper motions
