Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: GROWTH on S190510g: DECam Observation Planning and Follow-Up of a
  Distant Binary Neutron Star Merger Candidate   The first two months of the third Advanced LIGO and Virgo observing run (2019
April-May) showed that distant gravitational wave (GW) events can now be
readily detected. Three candidate mergers containing neutron stars (NS) were
reported in a span of 15 days, all likely located more than 100 Mpc away.
However, distant events such as the three new NS mergers are likely to be
coarsely localized, which highlights the importance of facilities and
scheduling systems that enable deep observations over hundreds to thousands of
square degrees to detect the electromagnetic counterparts. On 2019-05-10
02:59:39.292 UT the GW candidate S190510g was discovered and initially
classified as a BNS merger with 98% probability. The GW event was localized
within an area of 3462 deg2, later refined to 1166 deg2 (90%) at a distance of
227 +- 92 Mpc. We triggered Target of Opportunity observations with the Dark
Energy Camera (DECam), a wide-field optical imager mounted at the prime focus
of the 4m Blanco Telescope at CTIO in Chile. This Letter describes our DECam
observations and our real-time analysis results, focusing in particular on the
design and implementation of the observing strategy. Within 24 hours of the
merger time, we observed 65% of the total enclosed probability of the final
skymap with an observing efficiency of 94%. We identified and publicly
announced 13 candidate counterparts. S190510g was re-classified 1.7 days after
the merger, after our observations were completed, with a "binary neutron star
merger" probability reduced from 98% to 42% in favor of a "terrestrial"
classification.

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The categories of this paper are: supr-con
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The categories of this paper are: cond-mat
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th