疏散星团NGC2286的自行测定及成员研究

DETERMINATION OF PROPER MOTION AND MEMBERSHIP STUDY OF THE OPEN CLUSTER NGC2286

本文利用上海天文台40厘米天体照相仪拍摄的四对底片，测定了疏散星团NGC2286天区内2284颗恒星的相对自行及相应的误差。精度分析表明，百年自行的平均单位权中误差为±0″．366。详细的自行成员研究表明，星团的成员星很不确定，一种可能解释的是这个团也许并不存在，或者至少主目前已有的自行资料来说还无法对其作有效的成员判别。

Relative proper motions of 2284 stars and their corresponding errors in the region of the open cluster NGC2286 are determined from the four plate pairs, which were taken with the double astrograph with aperture of 40cm and focal length of 6.9m at Z-Sè Section of Shanghai Observatory. The epoch differences of the plate pairs are 38—69 years and the limiting magnitude is roughly 15. Errors of proper motions are found by intercomparing values of proper motions of the identical stars obtained from different pairs. It is shown from analysis that the typical mean error of centennial proper motions with unit weight is some ±0.″366. A detailed proper motion membership study has been made, which shows that there is no significant peak near to p=1, the maximum value of membership probabilities is less than 0.7, the number of stars with membership probabilities higher than 0.5 is much less than that of cluster stars obtained from solution of distribution parameters, and no clustering appearance in the surface distributions can be found for stars with different membership probability ranges. A possible explanation is that perharps the cluster NGC2286 does not exist, or it seems that for NGC2286 cluster stars can not yet been definitely separated from field stars only based upon the proper motion data presently available.