Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observations of the Ultra-compact X-ray Binary 4U 1543-624 in Outburst
  with NICER, INTEGRAL, Swift, and ATCA   We report on X-ray and radio observations of the ultra-compact X-ray binary
4U 1543-624 taken in August 2017 during an enhanced accretion episode. We
obtained NICER monitoring of the source over a $\sim10$ day period during which
target-of-opportunity observations were also conducted with Swift, INTEGRAL,
and ATCA. Emission lines were measured in the NICER X-ray spectrum at
$\sim0.64$ keV and $\sim6.4$ keV that correspond to O and Fe, respectively. By
modeling these line components, we are able to track changes in the accretion
disk throughout this period. The innermost accretion flow appears to move
inwards from hundreds of gravitational radii ($R_{g}=GM/c^{2}$) at the
beginning of the outburst to $<8.7$ $R_{g}$ at peak intensity. We do not detect
the source in radio, but are able to place a $3\sigma$ upper limit on the flux
density at $27$ $\mu$Jy beam$^{-1}$. Comparing the radio and X-ray
luminosities, we find that the source lies significantly away from the range
typical of black holes in the ${L}_{{r}}$-${L}_{{x}}$ plane, suggesting a
neutron star (NS) primary. This adds to the evidence that NSs do not follow a
single track in the ${L}_{{r}}$-${L}_{{x}}$ plane, limiting its use in
distinguishing between different classes of NSs based on radio and X-ray
observations alone.

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The categories of this paper are: hep-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
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The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: cs