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标题：The completeness-corrected rate of stellar encounters with the Sun from the first Gaiadata release ⋆
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作者：C. A. L. Bailer-Jones
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：609
DOI：10.1051/0004-6361/201731453
语种：English
出版社：EDP Sciences
摘要：I report on close encounters of stars to the Sun found in the firstGaiadata release (GDR1). CombiningGaiaastrometry 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 Hipparcosdata, even though the present study has many more candidates. This is partly because I reject stars with large radial velocity uncertainties (>10 km s-1), 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. TheGaiaastrometry predict a much closer passage than pre-Gaiaestimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 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 thisGaia-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 be545 ± 59 Myr-1. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds to87 ± 9 Myr-1within 2 pc. A more accurate analysis and assessment will be possible with futureGaiadata releases.
关键词：enOort cloudsolar neighborhoodstars: kinematics and dynamicssurveysmethods: statisticalmethods: analytical