Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Trigonometric parallaxes of two T dwarfs with Keck and ShaneAO
  astrometry   We present trigonometric parallax and proper motion measurements for two
T-type brown dwarfs. We derive our measurements from infrared laser guide star
adaptive optics observations spanning five years from the ShaneAO/SHARCS and
NIRC2/medium-cam instruments on the Shane and Keck telescopes, respectively. To
improve our astrometric precision, we measure and apply a distortion correction
to our fields for both instruments. We also transform the Keck and ShaneAO
astrometric reference frames onto the ICRS using five-parameter parallax and
proper motion solutions for background reference stars from Gaia DR2. Fitting
for parallax and proper motion, we measure parallaxes of $73.5\pm9.2$ mas and
$70.1\pm6.7$ mas for WISEJ19010703+47181688 (WISE1901) and
WISEJ21543294+59421370 (WISE2154), respectively. We utilize Monte Carlo methods
to estimate the error in our sparse field methods, taking into account
overfitting and differential atmospheric refraction. Comparing to previous
measurements in the literature, all of our parallax and proper motion values
fall within $2\sigma$ of the published measurements, and 4 of 6 measurements
are within $1\sigma$. These data are among the first parallax measurements of
these T dwarfs and serve as precise measurements for calibrating stellar
formation models. These two objects are the first results of an ongoing survey
of T dwarfs with Keck/NIRC2 and the Shane Adaptive Optics system at Lick
Observatory.

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The categories of this paper are: comp-gas
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
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The categories of this paper are: physics
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc