Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bright Star Astrometry with URAT   The U.S. Naval Observatory Robotic Astrometric Telescope (URAT) is observing
the northern sky since April 2012 for an astrometric survey. Multiple overlaps
per year are performed in a single bandpass (680$-$750 nm) using the "redlens"
20 cm aperture astrograph and a mosaic of large CCDs. Besides the regular, deep
survey to magnitude 18.5, short exposures with an objective grating are taken
to access stars as bright as 3rd magnitude. A brief overview of the program,
observing and reductions is given. Positions on the 8 to 20 mas level are
obtained of 66,202 Hipparcos stars at current epochs. These are compared to the
Hipparcos Catalog to investigate its accuracy. About 20\% of the observed
Hipparcos stars are found to have inconsitent positions with the Hipparcos
Catalog prediction on the 3 sigma level or over (about 75 mas or more
discrepant position offsets). Some stars are now seen at an arcsec (or 25
sigma) off their Hipparcos Catalog predicted position.

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The categories of this paper are: econ
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The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ex