天鹅臂II：Cam OB3中的一个年轻疏散星团
Stellar tracers of the Cygnus Arm. II: A young open cluster in Cam OB3
摘要：
Cam OB 3是唯一被认为属于外银河臂或天鹅座臂的OB星协。很少有成员被观测到，并且对该星协的距离模数也不清楚。我们试图更完整地描述凸轮OB 3的人口和更好地确定其距离模量。我们目前的紫外测光的O-型恒星BD +56 864和LS I +57 138周围的区域，发现一个明确的序列的早期类型的恒星，定义了一个未编目的疏散星团，我们称之为阿利坎特1。我们还提出了光谱的恒星在这个集群和周围的协会。从光谱类型的18个非常可能的成员协会和UBV测光发现在文献中，我们得出个人的红化，发现一个消光定律接近标准和平均距离模DM=13.0+-0.4。这个值是在很好的协议与距离模量的新集群阿利坎特1发现通过拟合光度序列的ZAMS。尽管有几颗O-型恒星存在，阿利坎特1是一个非常稀少的疏散星团，几乎完全没有早期的B-型恒星。我们的研究结果肯定了Cam OB 3位于天鹅臂上，并确定了第一个已知属于该协会的疏散星团。
英文摘要：
Cam OB3 is the only defined OB association believed to belong to the Outer Galactic Arm or Cygnus Arm. Very few members have been observed and the distance modulus to the association is not well known. We attempt a more complete description of the population of Cam OB3 and a better determination of its distance modulus. We present uvby photometry of the area surrounding the O-type stars BD +56 864 and LS I +57 138, finding a clear sequence of early-type stars that define an uncatalogued open cluster, which we call Alicante 1. We also present spectroscopy of stars in this cluster and the surrounding association. From the spectral types for 18 very likely members of the association and UBV photometry found in the literature, we derive individual reddenings, finding a extinction law close to standard and an average distance modulus DM=13.0+-0.4. This value is in excellent agreement with the distance modulus to the new cluster Alicante 1 found by fitting the photometric sequence to the ZAMS. In spite of the presence of several O-type stars, Alicante 1 is a very sparsely populated open cluster, with an almost total absence of early B-type stars. Our results definitely confirm Cam OB3 to be located on the Cygnus Arm and identify the first open cluster known to belong to the association.
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