Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Expansion of G11.2-0.3, a Radio Composite Supernova Remnant   We compare recent observations of the supernova remnant G11.2-0.3 taken with
the VLA during 2001-02 with images from VLA archives (1984-85) to detect and
measure the amount of expansion that has occurred during 17 years. The bright,
circular outer shell shows a mean expansion of (0.71 +/- 0.15)% and (0.50 +/-
0.17)%, from 20- and 6-cm data, respectively, which corresponds to a rate of
0.057' +/- 0.012'/yr at 20 cm and 0.040' +/- 0.013'/yr at 6 cm. From this
result, we estimate the age of the remnant to be roughly between 960 and 3400
years old, according to theoretical models of supernova evolution. This is
highly inconsistent with the 24000 yr characteristic age of PSR J1811-1925,
located at the remnant's center, but, rather, is consistent with the time since
the historical supernova observed in 386 AD. We also predict that G11.2-0.3 is
currently in a pre-Sedov evolutionary state, and set constraints on the
distance to the remnant based on Chandra X-ray spectral results.

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The categories of this paper are: adap-org
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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: dg-ga
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The categories of this paper are: cond-mat
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The categories of this paper are: acc-phys
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-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: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: chem-ph