The Pleiades and α Persei Clusters
The Pleiades and α Persei Clusters
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DOI：
10.1086/300533
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发表时间：
1998-10
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影响因子：
--
通讯作者：
O. Eggen
中科院分区：
文献类型：
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作者：
O. Eggen
昂宿星团和α英仙座星系团的上层主序成员被认为是地方协会的成员，产生的平均视差只比伊帕科斯观测的平均值大4%。(LOG TEF，MV)图显示，在6000K到8000K的温度范围内，毕宿四和α英仙座主序成员几乎相同，比昂宿星主序上的类似恒星亮十分之几。昂宿星团主序列的偏离既不能追溯到年龄，也不能追溯到被认为适用于这些星系团的范围内的重元素丰度差异。昂宿星氦丰度比毕宿星高出50%可能是造成光度差异的原因。另一种解释是昂宿星团被拒绝成为超星系团成员，和/或昂宿星团的依巴谷视差结果误差约10%。
The upper–main-sequence members of the Pleiades and α Persei clusters, considered as members of the Local Association, yield mean parallaxes that are only 4% larger than the mean values from Hipparcos observations. The (log Teff, MV) diagram reveals that in the temperature range from 6000 to 8000 K, the Hyades and α Persei main-sequence members are nearly identical and several tenths of a magnitude brighter than similar stars on the Pleiades main sequence. The departure of the Pleiades main sequence cannot be traced to either age or heavy-element abundance differences in the range thought to apply to these clusters. A 50% increase in the helium abundance of Pleiades over Hyades stars could account for the luminosity difference. Alternative explanations are that the Pleiades cluster is rejected from supercluster membership and/or that the Hipparcos parallax results for the Pleiades are in error by some 10%.