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arXiv 1612.02440astro-ph.SRastro-ph.GA
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盖亚DR1中的同动星：大量的非常宽的分离同动对

Comoving stars in Gaia DR1: An abundance of very wide separation co-moving pairs

Semyeong Oh, Adrian M. Price-Whelan, David W. Hogg, Timothy D. Morton, David N. Spergel

备注：
published in AJ with minor revision; A web visualization of the result is available at http://smoh.space/vis/gaia-comoving-stars
发表信息：
The Astronomical Journal 2017, 153, 257
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摘要：

{ \it盖亚}数据发布1的主要样本是第谷-盖亚天体测量解决方案（TGAS）：$\approx$ 200万个第谷-2源，相对于初始目录具有改进的松弛和自行。这种天文测量精度的提高为发现新的双星和运动的双星群提供了机会。我们寻找高置信度的同向运动对TGAS中的恒星，通过识别对恒星具有相同的三维速度，使用边缘化的似然比检验来区分候选人同向运动对从现场人口。虽然我们使用（偏差校正）逆视差作为距离的点估计来执行一些可视化，但似然比是用概率模型计算的，该模型包括视差和自行的协方差，并将恒星的（未知）真实距离和3D速度边缘化。我们在10，606颗独特的恒星中发现了13，085对共动恒星对，其分离度高达10 pc（我们的搜索极限）。其中一些对形成更大的群体，通过相互共动的邻居：这些对网络中的许多对应于已知的疏散星团和OB协会，但我们也报告了几个新的共动群体的发现。最令人惊讶的是，我们发现了大量的非常宽的（$>1$ pc）分离共动的恒星对，其数量随着分离的增加而增加，并且不能纯粹用假阳性污染来解释。我们的主要结果是一个目录的高置信度共动对的恒星在TGAS。我们讨论了这个目录的效用，使银河系的动力学推断，测试恒星大气模型，并验证化学丰度测量。

英文摘要：

The primary sample of the {\it Gaia} Data Release 1 is the Tycho-Gaia Astrometric Solution (TGAS): $\approx$ 2 million Tycho-2 sources with improved parallaxes and proper motions relative to the initial catalog. This increased astrometric precision presents an opportunity to find new binary stars and moving groups. We search for high-confidence comoving pairs of stars in TGAS by identifying pairs of stars consistent with having the same 3D velocity using a marginalized likelihood ratio test to discriminate candidate comoving pairs from the field population. Although we perform some visualizations using (bias- corrected) inverse parallax as a point estimate of distance, the likelihood ratio is computed with a probabilistic model that includes the covariances of parallax and proper motions and marginalizes the (unknown) true distances and 3D velocities of the stars. We find 13,085 comoving star pairs among 10,606 unique stars with separations as large as 10 pc (our search limit). Some of these pairs form larger groups through mutual comoving neighbors: many of these pair networks correspond to known open clusters and OB associations, but we also report the discovery of several new comoving groups. Most surprisingly, we find a large number of very wide ($>1$ pc) separation comoving star pairs, the number of which increases with increasing separation and cannot be explained purely by false-positive contamination. Our key result is a catalog of high-confidence comoving pairs of stars in TGAS. We discuss the utility of this catalog for making dynamical inferences about the Galaxy, testing stellar atmosphere models, and validating chemical abundance measurements.

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