Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray Spectroscopy of the gamma-ray Brightest Nova V906 Car
  (ASASSN-18fv)   Shocks in gamma-ray emitting classical novae are expected to produce bright
thermal and non-thermal X-rays. We test this prediction with simultaneous
NuSTAR and Fermi/LAT observations of nova V906 Car, which exhibited the
brightest GeV gamma-ray emission to date. The nova is detected in hard X-rays
while it is still gamma-ray bright, but contrary to simple theoretical
expectations, the detected 3.5-78 keV emission of V906 Car is much weaker than
the simultaneously observed >100 MeV emission. No non-thermal X-ray emission is
detected, and our deep limits imply that the gamma-rays are likely hadronic.
After correcting for substantial absorption (N_H ~ 2 x 10^23 cm^-2), the
thermal X-ray luminosity (from a 9 keV optically-thin plasma) is just ~2% of
the gamma-ray luminosity. We consider possible explanations for the low thermal
X-ray luminosity, including the X-rays being suppressed by corrugated,
radiative shock fronts or the X-rays from the gamma-ray producing shock are
hidden behind an even larger absorbing column (N_H >10^25 cm^-2). Adding
XMM-Newton and Swift/XRT observations to our analysis, we find that the
evolution of the intrinsic X-ray absorption requires the nova shell to be
expelled 24 days after the outburst onset. The X-ray spectra show that the
ejecta are enhanced in nitrogen and oxygen, and the nova occurred on the
surface of a CO-type white dwarf. We see no indication of a distinct super-soft
phase in the X-ray lightcurve, which, after considering the absorption effects,
may point to a low mass of the white dwarf hosting the nova.

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The categories of this paper are: hep-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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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: funct-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin