CCD photometry and proper motions of late-type stars in the young open cluster Stock 2.
FOSTER D.C., THEISSEN A., BUTLER C.J., ROLLESTON W.R.J., BYRNE P.B. and HAWLEY S.L.
Abstract (from CDS):
We present the results of the first CCD BVRI photometric and proper motion study of late-type stars in the young open cluster Stock 2. Twenty-one fields of approximately 5'x5' size have been observed photometrically, from which we have identified 118 candidate members based on their positions on colour-magnitude diagrams relative to theoretical isochrones. From a comparison of the known star density of the Pleiades, we estimate the contamination of this selection process due to background stars to be as large as ∼50%. However, only 22 of those 118 candidate members have proper motions consistent with membership, suggesting that the contamination is of the order of 80%. Additional candidate members were found by means of a proper motion analysis of Schmidt plate material for a 3°x3° field containing the cluster. The cluster proper motion allows us to separate members from background and foreground stars. We have found 634 stars with a membership probability ≥50% down to a limiting magnitude of B≃20, corresponding to late-M dwarfs at the distance of Stock 2.