Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the accuracy of close stellar approaches determination   The aim of this paper is to demonstrate the accuracy of our knowledge of
close stellar passage distances in the pre-GAIA era.We used the most precise
astrometric and kinematic data available at the moment and prepared a list of
40 stars nominally passing (in the past or future) closer than 2 pc from the
Sun.We used a full gravitational potential of the Galaxy to calculate the
motion of the Sun and a star from their current positions to the proximity
epoch. For this calculations we used a numerical integration in rectangular,
Galactocentric coordinates. We showed that in many cases the numerical
integration of the star motion gives significantly different results than
popular rectilinear approximation.We found several new stellar candidates for
close visitors in past or in future. We used a covariance matrices of the
astrometric data for each star to estimate the accuracy of the obtained
proximity distance and epoch. To this aim we used a Monte Carlo method,
replaced each star with 10 000 of its clones and studied the distribution of
their individual close passages near the Sun. We showed that for contemporary
close neighbours the precision is quite good but for more distant stars it
strongly depends on the quality of astrometric and kinematic data. Several
examples are discussed in detail, among them the case of HIP 14473. For this
star we obtained the nominal proximity distance as small as 0.22 pc 3.78 Myr
ago. However there exist strong need for more precise astrometry of this star
since the proximity point uncertainty is unacceptably large.

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The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
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The categories of this paper are: stat