Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cas A: The Bright X-ray Knots and Oxygen Emission   Chandra High-Energy Transmission Grating (HETG) X-ray spectra are extracted
from 17 bright, narrow regions of Cas A and provide unique measurements of
their kinematic and plasma states. From the dominant emission lines, e.g.
He-like Si, we derive accurate Doppler shifts in the range -2500 to +4000 km/s;
these agree well with transverse-velocity measurements and allow the features
to be located in 3D. Plasma diagnostics of these regions indicate temperatures
largely around 1 keV with some above 3 keV. Using as well the non-dispersed
zeroth-order data, we determine NEI model parameters for the regions which lead
to density estimates. Values of n_e ~ 100 /cm^3 are likely the maximum of a
range of densities in this X-ray emitting material. The common "oxygen-rich"
assumption is coarsely tested by comparing the integrated O VIII line flux and
continuum levels. It appears that most of the continuum is due to another
source, e.g., from He.

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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
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The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex