Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Truncation of the Accretion Disk at One Third of the Eddington Limit in
  the Neutron Star Low-Mass X-ray Binary Aquila X-1   We perform a reflection study on a new observation of the neutron star
low-mass X-ray binary Aquila X-1 taken with NuSTAR during the August 2016
outburst and compare with the July 2014 outburst. The source was captured at
$\sim32\%\ L_{\mathrm{Edd}}$, which is over four times more luminous than the
previous observation during the 2014 outburst. Both observations exhibit a
broadened Fe line profile. Through reflection modeling, we determine that the
inner disk is truncated $R_{in,\ 2016}=11_{-1}^{+2}\ R_{g}$ (where
$R_{g}=GM/c^{2}$) and $R_{in,\ 2014}=14\pm2\ R_{g}$ (errors quoted at the 90%
confidence level). Fiducial neutron star parameters (M$_{NS}=1.4$ M$_{\odot}$,
$R_{NS}=10$ km) give a stellar radius of $R_{NS}=4.85\ R_{g}$; our measurements
rule out a disk extending to that radius at more than the $6\sigma$ level of
confidence. We are able to place an upper limit on the magnetic field strength
of $B\leq3.0-4.5\times10^{9}$ G at the magnetic poles, assuming that the disk
is truncated at the magnetospheric radius in each case. This is consistent with
previous estimates of the magnetic field strength for Aquila X-1. However, if
the magnetosphere is not responsible for truncating the disk prior to the
neutron star surface, we estimate a boundary layer with a maximum extent of
$R_{BL,\ 2016}\sim10\ R_{g}$ and $R_{BL,\ 2014}\sim6\ R_{g}$. Additionally, we
compare the magnetic field strength inferred from the Fe line profile of Aquila
X-1 and other neutron star low-mass X-ray binaries to known accreting
millisecond X-ray pulsars.

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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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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: adap-org
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The categories of this paper are: funct-an
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The categories of this paper are: acc-phys