Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Astrometry of OH/IR stars using 1612 MHz hydroxyl masers. I. Annual
  parallaxes of WX Psc and OH138.0+7.2   We report on the measurement of the trigonometric parallaxes of 1612 MHz
hydroxyl masers around two asymptotic giant branch stars, WX Psc and
OH138.0+7.2, using the NRAO Very Long Baseline Array with in-beam phase
referencing calibration. We obtained a 3-sigma upper limit of <=5.3 mas on the
parallax of WX Psc, corresponding to a lower limit distance estimate of >~190
pc. The obtained parallax of OH138.0+7.2 is 0.52+/-0.09 mas (+/-18%),
corresponding to a distance of 1.9(+0.4,-0.3) kpc, making this the first
hydroxyl maser parallax below one milliarcsecond. We also introduce a new
method of error analysis for detecting systematic errors in the astrometry.
Finally, we compare our trigonometric distances to published phase-lag
distances toward these stars and find a good agreement between the two methods.

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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: atom-ph