Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: ASCA Observation of the Lyman-limit Quasar PKS2145+067   X-ray observation of a famous Lyman-limit quasar PKS2145+067at z_em= 0.990
was carried with ASCA. The source showed a 2-10 keV flux of 1.3 E-11 erg cm^-2
sec^-1 (L_X = 2.5 E46 erg sec^-1 for H_0=50 km s^-1 Mpc^-1) described by a
power-law spectrum with a photon index Gamma=1.63 +/- 0.04 . In the ASCA energy
band, no excess absorption was detected implying the absorption column density
at z_ ab=0.791 was less than 1.6 E21 cm^-2 if absorbing medium had a metal
abundance of 0.5 solar. Comparison with previous Einstein and ROSAT
observations shows that PKS2145+067 has increased its luminosity by a factor of
2--3 between 1991 and 1998.

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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: comp-gas
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The categories of this paper are: supr-con
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
7
The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex