WIYN Open Cluster Study. LV. Astrometry and Membership in NGC 6819
The Astronomical Journal, Volume 146, Issue 2, article id. 43, 12 pp. (2013).
Published in Aug 2013
We present proper motions and astrometric membership analysis for 15,750 stars around the intermediate-age open cluster NGC 6819. The accuracy of relative proper motions for well-measured stars ranges from ~0.2 mas yr-1 within 10' of the cluster center to 1.1 mas yr-1 outside this radius. In the proper motion vector-point diagram, the separation between the cluster members and field stars is convincing down to V ~ 18 and within 10' from the cluster center. The formal sum of membership probabilities indicates a total of ~2500 cluster members down to V ~ 22. We confirm the cluster membership of several variable stars, including some eclipsing binaries. The estimated absolute proper motion of NGC 6819 is \mu _x^abs=-2.6+/- 0.5 and \mu _y^abs=-4.2+/- 0.5 mas yr-1. A cross-identification between the proper motion catalog and a list of X-ray sources in the field of NGC 6819 resulted in a number of new likely optical counterparts, including a candidate CV. For the first time we show that there is significant differential reddening toward NGC 6819.Based on observations collected at the Canada-France-Hawaii Telescope.
astrometry; open clusters and associations: individual: NGC 6819