We present results from 13776 radial-velocity (RV) measurements of 1278 candidate members of the old (4 Gyr) open cluster M67 (NGC 2682). The measurements are the results of a long-term survey that includes data from seven telescopes with observations for some stars spanning over 40 years. For narrow-lined stars, RVs are measured with precisions ranging from about 0.1 to 0.8 km s?1. The combined stellar sample reaches from the brightest giants in the cluster down to about 4 mag below the main-sequence turnoff (), covering a mass range of about 1.34 to 0.76 . Spatially, the sample extends to a radus of 30 arcmin (7.4 pc in projection at a distance of 850 pc or 6–7 core radii). We find M67 to have a mean RV of km s?1 (with an internal precision of ±0.03 km s?1) well separated from the mean velocity of the field. For stars with measurements, we derive RV membership probabilities and identify RV variables, finding 562 cluster members, 142 of which show significant RV variability. We use these cluster members to construct a color–magnitude diagram and identify a rich sample of stars that lie far from the standard single star isochrone, including the well-known blue stragglers, sub-subgiants and yellow giants. These exotic stars have a binary frequency of (at least) 80%, more than three times that detected for stars in the remainder of the sample. We confirm that the cluster is mass segregated, finding the binaries to be more centrally concentrated than the single stars in our sample at the 99.8% confidence level (and at the 98.7% confidence level when only considering main-sequence stars). The blue stragglers are centrally concentrated as compared to the solar-type main-sequence single stars in the cluster at the 99.7% confidence level. Accounting for measurement precision, we derive an RV dispersion in M67 of 0.80 ± 0.04 km s?1 for our sample of single main-sequence stars, subgiants and giants with . When corrected for undetected binaries, this sample yields a true RV dispersion of km s?1. The radial distribution of the velocity dispersion is consistent with an isothermal distribution within our stellar sample. Using the cluster RV dispersion, we estimate a virial mass for the cluster of .
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机译：我们目前的结果来自旧的（4 Gyr）开放星团M67（NGC 2682）的1278个候选成员的13776个径向速度（RV）测量。这些测量是长期调查的结果，其中包括来自七个望远镜的数据以及对40年以上恒星的观测。对于窄线恒星，RVs的测量精度约为0.1至0.8 km s？1。合并的恒星样本从星团中最亮的巨星降到主序列截止点（）以下约4 mag，覆盖的质量范围约为1.34至0.76。在空间上，样本延伸到30 arcmin的半径（投影7.4 pc，投影距离为850 pc或6–7核心半径）。我们发现M67的平均RV为km s？1（内部精度为±0.03 km s？1），与磁场的平均速度完全分开。对于具有测量值的恒星，我们推导出RV成员概率并识别RV变量，找到562个簇成员，其中142个簇显示出显着的RV变异性。我们使用这些星团成员来构建一个色度图，并确定大量远离标准单星等时线的恒星样本，其中包括著名的蓝色散流星，亚亚变星和黄色巨星。这些奇异恒星的双星频率为（至少）80％，是样本其余部分中检测到的恒星的三倍以上。我们确认星团是质量隔离的，发现在我们的样本中，双星比样本中的单个星更集中地集中在99.8％的置信度下（而仅考虑主序星的置信度在98.7％的置信度下）。与散布在星团中的太阳型主序单星相比，蓝色散落者集中在99.7％的置信度上。考虑到测量精度，对于单个主序恒星，副超星和巨星样本，我们得出M67的RV色散为0.80±0.04 km s？1。当校正未检测到的二进制文件时，该样本将产生km s？1的真实RV色散。速度色散的径向分布与我们恒星样本中的等温分布一致。使用簇RV分散，我们估算的簇的病毒质量。
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