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Astron. Astrophys. Suppl. Ser. 143, 409-420

CCD photometry and proper motions of late-type stars in the young open cluster Stock 2

D.C. Foster 1 - A. Theissen1 - C.J. Butler 1 - W.R.J. Rolleston 2 - P.B. Byrne 1 - S.L. Hawley 3

Send offprint request: A. Theissen

1 - Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
2 - Department of Pure and Applied Physics, The Queen's University of Belfast, Belfast BT7 1NN, N. Ireland
3 - Department of Physics and Astronomy, Michigan State University, E. Lansing, Michigan 48824, U.S.A.

Received December 8, 1998; accepted February 8, 2000


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 $5'\times 5'$ 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 $\sim50\%$. 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 $3^{\circ}\times 3^{\circ}$ 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 $\ge 50\%$ down to a limiting magnitude of $B \approx 20$, corresponding to late-M dwarfs at the distance of Stock 2[*].

Key words: stars: evolution -- stars: late-type -- open clusters: individual; stock 2

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