Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the
  Blast Wave of Supernova 1987A   Multiwavelength observations of supernova remnant (SNR) 1987A show that its
morphology and luminosity are rapidly changing at X-ray, optical, infrared, and
radio wavelengths as the blast wave from the explosion expands into the
circumstellar equatorial ring, produced by mass loss from the progenitor star.
The observed infrared (IR) radiation arises from the interaction of dust grains
that formed in mass outflow with the soft X-ray emitting plasma component of
the shocked gas. Spitzer IRS spectra at 5 - 30 microns taken on day 6190 since
the explosion show that the emission arises from ~ 1.1E-6 Msun of silicate
grains radiating at a temperature of ~180+20-15 K. Subsequent observations on
day 7137 show that the IR flux had increased by a factor of 2 while maintaining
an almost identical spectral shape. The observed IR-to-X-ray flux ratio (IRX)
is consistent with that of a dusty plasma with standard Large Magellanic Cloud
dust abundances. IRX has decreased by a factor of ~ 2 between days 6190 and
7137, providing the first direct observation of the ongoing destruction of dust
in an expanding SN blast wave on dynamic time scales. Detailed models
consistent with the observed dust temperature, the ionization timescale of the
soft X-ray emission component, and the evolution of IRX suggest that the
radiating silicate grains are immersed in a 3.5E6 K plasma with a density of
(0.3-1)E4 cm^{-3}, and have a size distribution that is confined to a narrow
range of radii between 0.023 and 0.22 microns. Smaller grains may have been
evaporated by the initial UV flash from the supernova.

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The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
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The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: supr-con
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The categories of this paper are: math
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: eess
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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: q-fin
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The categories of this paper are: hep-lat