差异变红球状星团NGC 3201中恒星星族不均匀性的证据
Evidence of the inhomogeneity of the stellar population in the differentially reddened globular cluster NGC 3201
摘要：
我们报告的证据的不均匀性（多重性）的恒星星族在银河系球状星团（GC）NGC 3201，这是不规则的红色在其脸上。我们进行了更详细和仔细的分析，我们最近发表的新的多色测光在一个广泛的领域的集群，特别强调的U带。利用校正了微分红化的光度数据，我们首次发现了星团恒星星族不均匀性和GC径向变化的两个关键标志。这是：（1）在红巨星支星（U-B）色指数的色位图上，有一个明显的趋势，即离星团中心越远，其（U-B）色平均值越蓝;（2）星团中次巨星分支（SGB）星的径向分布与它们的U星等的关系，其中较亮的恒星比它们较暗的对应物在置信水平上集中得更少，置信水平在99.2%和99.9%之间变化，这取决于用于选择恒星的颜色指数。我们最近在GC NGC 1261中发现了同样的效应。然而，与NGC 1261相反，我们无法明确地指出SGB/RGB恒星的哪一个子种群可以是星团中蓝色和红色水平分支恒星的祖先。除了M4之外，NGC 3201是另一个很可能具有不均匀恒星星族的GC，它的质量比最大质量的银河系GC要低，在那里首次明确地发现了多个恒星星族
英文摘要：
We report on evidence of the inhomogeneity (multiplicity) of the stellar population in the Galactic globular cluster (GC) NGC 3201, which is irregularly reddened across its face. We carried out a more detailed and careful analysis of our recently published new multi-color photometry in a wide field of the cluster with particular emphasis on the U band. Using the photometric data corrected for differential reddening, we found for the first time two key signs of the inhomogeneity in the cluster's stellar population and of its radial variation in the GC. These are (1) an obvious trend in the color-position diagram, based on the (U-B) color-index, of red giant branch (RGB) stars, which shows that the farther from the cluster's center, the bluer on average the (U-B) color of the stars is; and (2) the dependence of the radial distribution of sub-giant branch (SGB) stars in the cluster on their U magnitude, where brighter stars are less centrally concentrated than their fainter counterparts at a confidence level varying between 99.2% and 99.9% depending on the color-index used to select the stars. The same effects were recently found by us in the GC NGC 1261. However, contrary to NGC 1261, we are not able to unambiguously suggest which of the sub-populations of SGB/RGB stars can be the progenitor of blue and red horizontal branch stars of the cluster. Apart from M4, NGC 3201 is another GC very probably with an inhomogeneous stellar population, which has essentially lower mass than the most massive Galactic GCs where multiple stellar populations were unambiguously detected for the first time
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