论文标题
银河OB组的Villafranca目录：I。具有O2-O3.5星的系统
The Villafranca catalog of Galactic OB groups: I. Systems with O2-O3.5 stars
论文作者
论文摘要
语境。 Goss光谱分类和GAIA数据显着提高了我们测量距离并确定具有OB恒星恒星群体的成员身份的能力。目标。我们已经启动了一个计划，以识别，测量距离并确定带有OB星的银河恒星群的成员。我们从具有O恒星组的组的识别和距离确定开始。在本文中，我们集中于包含最早光谱亚型的恒星的组。方法。我们使用戈斯选择具有O2-O3.5星的银河系恒星组，以及一种结合Gaia Dr2光度法，位置，适当运动和视差的方法，以分配强大的成员身份和测量距离。我们还在该论文中包括两个簇，以生成我们的第一个O型银河系恒星组的第一个列表。结果。我们得出距离，确定会员资格，并分析具有O星，Villafranca O-001至O-016的16个银河恒星群的结构，其中包括最早以最早的O-O-Type光学上可接近的星星而闻名的14组。我们将距离与以前的结果进行比较，并确定最佳一致性是与VLBI视差，最糟糕的是运动距离。我们的结果表明，大型恒星可以在相对较低的质量簇中甚至在近距离化中形成，就像北美星云的Bajamar Star一样。这为恒星形成的分层场景提供了支持，其中有些恒星出生在定义明确的绑定群集中，而另一些则出生于从一开始就没有束缚的协会中：新生儿群体的形状和大小都有多种形状和大小。我们建议HD 64 568和HD 64 315 AB可能同时从Villafranca O-012 S射出。我们的结果与大约的差异一致。盖亚DR2中的20 microas在明亮和微弱的恒星之间可视零点。 （简略）
CONTEXT. The GOSSS spectral classifications and Gaia data have significantly improved our ability to measure distances and determine memberships of stellar groups with OB stars. AIMS. We have started a program to identify, measure distances, and determine the membership of Galactic stellar groups with OB stars. We start with the identification and distance determinations of groups with O stars. In this paper we concentrate on groups that contain stars with the earliest spectral subtypes. METHODS. We use GOSSS to select Galactic stellar groups with O2-O3.5 stars and a method that combines Gaia DR2 photometry, positions, proper motions, and parallaxes to assign robust memberships and measure distances. We also include the two clusters in that paper to generate our first list of 16 O-type Galactic stellar groups. RESULTS. We derive distances, determine the membership, and analyze the structure of sixteen Galactic stellar groups with O stars, Villafranca O-001 to O-016, including the 14 groups with the earliest-O-type optically-accessible stars known in the Milky Way. We compare our distance with previous results and establish that the best consistency is with VLBI parallaxes and the worst is with kinematic distances. Our results indicate that massive stars can form in relatively low-mass clusters or even in near-isolation, as is the case for the Bajamar star in the North America nebula. This lends support to the hierarchical scenario of star formation, where some stars are born in well-defined bound clusters but others are born in associations that are unbound from the beginning: groups of newborn stars come in many shapes and sizes. We propose that HD 64 568 and HD 64 315 AB could have been ejected simultaneously from Villafranca O-012 S. Our results are consistent with a difference of approx. 20 microas in the Gaia DR2 parallax zero point between bright and faint stars. (ABRIDGED)
