Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Near-infrared spectral evolution of the Type Ia supernova 2014J in the
  nebular phase: implications for the progenitor system   As the closest Type Ia supernova in decades, SN 2014J provides a unique
opportunity for detailed investigation into observational signatures of the
progenitor system and explosion mechanism in addition to burning product
distribution. We present a late-time near-infrared spectral series from
Gemini-N at $307-466$ days after the explosion. Following the $H$-band
evolution probes the distribution of radioactive iron group elements, the
extent of mixing, and presence of magnetic fields in the expanding ejecta.
Comparing the isolated $1.6440$ $\mu$m [Fe II] emission line with synthetic
models shows consistency with a Chandrasekhar-mass white dwarf of
$\rho_c=0.7\times10^9$ g cm${}^{-3}$ undergoing a delayed detonation. The ratio
of the flux in the neighboring $1.54$ $\mu$m emission feature to the flux in
the $1.6440$ $\mu$m feature shows evidence of some limited mixing of stable and
radioactive iron group elements in the central regions. Additionally, the
evolution of the $1.6440$ $\mu$m line shows an intriguing asymmetry. When
measuring line-width of this feature, the data show an increase in line width
not seen in the evolution of the synthetic spectra, corresponding to
$\approx1{,}000$ km s${}^{-1}$, which could be caused by a localized transition
to detonation producing asymmetric ionization in the ejecta. Using the
difference in width between the different epochs, an asymmetric component in
the central regions, corresponding to approximately the inner $2\times10^{-4}$
of white dwarf mass suggests an off-center ignition of the initial explosion
and hence of the kinematic center from the chemical center. Several additional
models investigated, including a He detonation and a merger, have difficulty
reproducing the features seen these spectra.

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The categories of this paper are: stat
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: adap-org
2
The categories of this paper are: math