5 Conclusions

BVRI CCD photometry has been obtained for 21 $5\times$ 5 arcmin fields in the region of Stock 2. From a photometric selection using two colour-magnitude diagrams, 118 candidate cluster members have been identified. These range from V=14.2 to V=20.4, corresponding to spectral type from mid-K to late-M. We compared these results with the observed luminosity and mass-distribution functions for the Pleiades (Hambly & Jameson [1991]). After scaling the distance modulus of the Pleiades to Stock 2, our CCD study would have resulted in the detection of 52 Pleiads. Since we found 118 Stock 2 member candidates, the contamination of this sample was estimated to be roughly 50%. This comparison is justified by Lynga's ([1987]) classification of "richness index'' for both clusters. However, the richness index is a rough classification based on the observed number of early-type stars in clusters, and the mass-distribution of late-type stars may be different.

The results of a proper motion survey of Stock 2 are also presented. The survey covered an area of $3^{\circ}\times 3^{\circ}$ about the nominal cluster centre. The selection of candidate cluster members was based on an initial selection from a photographically determined colour-magnitude diagram. The analysis identified 634 stars with magnitudes from B=12.8 to $B\sim 20$. The contamination of the sample was estimated to range from < 20% in the brightest bin to > 40% in the faintest bin.

The results of the proper motion analysis were also applied to the CCD determined candidate members. Of the 118 selected stars, 22 have proper motions consistent with cluster membership, with perhaps only one or two field stars present in the list. This is less than half of the expected number of cluster members in the area covered by the CCD photometry, estimated from comparison with the Pleiades. This suggests that while both clusters have the same "richness index'', the core of Stock 2 contains fewer stars than the core of the Pleiades.

Acknowledgements

We gratefully acknowledge the help and assistance of Nigel Hambly in reducing and analysing the proper motion data. Data reduction was performed on the PPARC funded Northern Ireland STARLINK node. DCF acknowledges support of a studentship from Armagh observatory. Research at Armagh Observatory is funded by a grant-in-aid from DENI. AT acknowledges support from PPARC grants GR/J25352, GR/L21594 and GR/L29859. WRJR also acknowledges financial assistence from the PPARC. SLH acknowledges partial support from NSF grant # AST94-57455.