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arXiv 1708.08595astro-ph.SRastro-ph.EP
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从第一个盖亚数据发布的恒星与太阳相遇的完整性校正率

The completeness-corrected rate of stellar encounters with the Sun from the first Gaia data release

C. A. L. Bailer-Jones

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摘要：

我报告了在第一次盖亚数据发布（GDR 1）中发现的恒星与太阳的近距离接触。结合盖亚天体测量与径向速度约320 000恒星从各种目录，我整合轨道在银河系的潜力，以确定这些恒星通过在几个秒差距。这样的遭遇可能会影响太阳系，例如通过奥尔特云的引力扰动。16颗恒星被发现在2pc以内（尽管其中一些数据可疑）。这比基于依巴谷数据的类似研究中发现的要少，尽管目前的研究有更多的候选者。这部分是因为我拒绝了具有大径向速度不确定性（> 10 km/s）的恒星，部分是因为GDR 1中缺少恒星（特别是在明亮的一端）。最近的一次发现是Gl 710，一颗K矮星，在大约130万年前接近太阳。盖亚天体测量预测比前盖亚估计更近的通道，然而：只有16000 AU（90%置信区间：10000至21000 AU），这将使这颗恒星在奥尔特云内。使用一个简单的模型的空间，速度和光度分布的恒星，连同近似的观测选择函数，我模型的不完整性，这个盖亚为基础的搜索作为一个函数的时间和距离最近的办法。将此应用于观测到的相遇的一个子集（不包括重复和速度大得令人难以置信的恒星），我估计在过去和未来500万年的平均5pc内的恒星相遇率为545 +/-59每百万年。假设在一定的遭遇距离内（我的模型预测的），这对应于87 +/-9每我在2 pc。更准确的分析和评估将有可能与未来的盖亚数据发布。

英文摘要：

I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which pass within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars with large radial velocity uncertainties (>10 km/s), and partly because of missing stars in GDR1 (especially at the bright end). The closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000 to 21 000 AU), which will bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be 545 +/- 59 per Myr. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds to 87 +/- 9 per My within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.

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