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

¹ Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland e-mail: ath@star.arm.ac.uk
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.

Send offprint request to: A. Theissen

Received: 8 December 1998
Accepted: 8 February 2000

Abstract


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 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 . However, only 22 of those 118 candidate members have proper motions consistent with membership, suggesting that the contamination is of the order of . 
Additional candidate members were found by means of a proper motion analysis of Schmidt plate material for a 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 down to a limiting magnitude of , corresponding to late–M dwarfs at the distance of Stock 2.