Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: VLBI Imagings of Kilo-parsec Knot in 3C 380   We investigate observational properties of a kilo-parsec scale knot in
radio-loud quasar 3C 380 by using two epoch archival data obtained by Very Long
Baseline Interferometry (VLBI) at 5 GHz on 1998 July and 2001 April. We succeed
in obtaining the highest spatial resolution image of the bright knot K1 located
at 732 milliarcseconds, or more than 20 kpc de-projected, downstream from the
nucleus three times better than previously obtained highest resolution image by
Papageorgiou et al. (2006). Our images reveal, with new clarity, "inverted
bow-shock" structure in K1 facing the nucleus and its morphology resembles a
conical shock wave. By comparing the two epoch images directly, we explore the
kinematics of K1 and obtain the upper limit of apparent velocity, 0.25 mas/yr
or 9.8 c of K1 for the first time. The upper limit of apparent velocity is
marginally smaller than superluminal motions seen in the core region. Further
new epoch VLBI observations are necessary to measure the proper motion at K1.

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The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
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The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
2
The categories of this paper are: math