Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lord of the Rings: A Kinematic Distance to Circinus X-1 from a Giant
  X-Ray Light Echo   Circinus X-1 exhibited a bright X-ray flare in late 2013. Follow-up
observations with Chandra and XMM-Newton from 40 to 80 days after the flare
reveal a bright X-ray light echo in the form of four well-defined rings with
radii from 5 to 13 arcminutes, growing in radius with time. The large fluence
of the flare and the large column density of interstellar dust towards Circinus
X-1 make this the largest and brightest set of rings from an X-ray light echo
observed to date. By deconvolving the radial intensity profile of the echo with
the MAXI X-ray lightcurve of the flare we reconstruct the dust distribution
towards Circinus X-1 into four distinct dust concentrations. By comparing the
peak in scattering intensity with the peak intensity in CO maps of molecular
clouds from the Mopra Southern Galactic Plane CO Survey we identify the two
innermost rings with clouds at radial velocity ~ -74 km/s and ~ -81 km/s,
respectively. We identify a prominent band of foreground photoelectric
absorption with a lane of CO gas at ~ -32 km/s. From the association of the
rings with individual CO clouds we determine the kinematic distance to Circinus
X-1 to be $D_{Cir X-1} = 9.4^{+0.8}_{-1.0}$ kpc. This distance rules out
earlier claims of a distance around 4 kpc, implies that Circinus X-1 is a
frequent super-Eddington source, and places a lower limit of $\Gamma \gtrsim
22$ on the Lorentz factor and an upper limit of $\theta_{jet} \lesssim
3^{\circ}$ on the jet viewing angle.

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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: q-alg
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The categories of this paper are: hep-lat
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The categories of this paper are: cond-mat
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an