Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stellar occultations enable milliarcsecond astrometry for
  Trans-Neptunian objects and Centaurs   Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary
system formation, and their physical properties have invaluable information for
evolutionary theories. Stellar occultation is a ground-based method for
studying these small bodies and has presented exciting results. These
observations can provide precise profiles of the involved body, allowing an
accurate determination of its size and shape. The goal is to show that even
single-chord detections of TNOs allow us to measure their milliarcsecond
astrometric positions in the reference frame of the Gaia second data release
(DR2). Accurated ephemerides can then be generated, allowing predictions of
stellar occultations with much higher reliability. We analyzed data from
stellar occultations to obtain astrometric positions of the involved bodies.
The events published before the Gaia era were updated so that the Gaia DR2
catalog is the reference. Previously determined sizes were used to calculate
the position of the object center and its corresponding error with respect to
the detected chord and the International Celestial Reference System (ICRS)
propagated Gaia DR2 star position. We derive 37 precise astrometric positions
for 19 TNOs and 4 Centaurs. Twenty-one of these events are presented here for
the first time. Although about 68\% of our results are based on single-chord
detection, most have intrinsic precision at the submilliarcsecond level. Lower
limits on the diameter and shape constraints for a few bodies are also
presented as valuable byproducts. Using the Gaia DR2 catalog, we show that even
a single detection of a stellar occultation allows improving the object
ephemeris significantly, which in turn enables predicting a future stellar
occultation with high accuracy. Observational campaigns can be efficiently
organized with this help, and may provide a full physical characterization of
the involved object.

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The categories of this paper are: eess
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg