Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High-resolution X-ray spectroscopy of the low and high states of the
  Seyfert 1 galaxy NGC 4051 with Chandra LETGS   Methods. We analyse two observations taken with the Low Energy Transmission
Grating Spectrometer of Chandra. We investigated the spectral response to a
sudden flux decrease by a factor of 5, which occurred during the second
observation. Results. We detect a highly ionised absorption component with an
outflow velocity of -4670 km/s, one of the highest outflow velocity components
observed in a Seyfert 1 galaxy. The spectra contain a relativistic O VIII Ly
alpha line, and four absorption components spanning a range in ionisation
parameter xi between 0.07 and 3.19. An emission component producing radiative
recombination continua of C VI and C V appears during the low state. The black
body temperature decreases with the drop in flux observed in the second
observation. Conclusions. For all absorber components we exclude that the
ionisation parameter linearly responded to the decrease in flux by a factor of
5. The variability of the absorber suggest that at least three out of four
detected components are located in the range 0.02-1 pc. ABRIDGED

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The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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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: chao-dyn