Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: XMM-Newton spectroscopy of high redshift quasars   We present XMM-Newton X-ray spectra and optical photometry of four high
redshift (z=2.96-3.77) quasars, [HB89] 0438-436, [HB89] 2000-330, [SP89]
1107+487 and RX J122135.6+280613; of these four objects the former two are
radio-loud, the latter two radio-quiet. Model fits require only a power law
with Galactic absorption in each case; additional intrinsic absorption is also
needed for [HB89] 0438-436 and RX J122135.6+280613. The spectra are hard (Gamma
\~1.7 for [HB89] 0438-436, [HB89] 2000-330 and ~1.4 for RX J122135.6+280613)
with the exception of [SP89]~1107+487 which is softer (Gamma ~2.0); the
combined Galactic and intrinsic absorption of lower energy X-rays in the latter
source is much less significant than in the other three. The two intrinsically
unabsorbed sources have greater optical fluxes relative to the X-ray
contributions at the observed energies. While there is no need to include
reflection or iron line components in the models, our derived upper limits (99%
confidence) on these parameters are not stringent; the absence of these
features, if confirmed, may be explained in terms of the high power law
contribution and/or a potentially lower albedo due to the low disc temperature.
However, we note that the power-law spectrum can be produced via mechanisms
other than the Comptonization of accretion disc emission by a corona; given
that all four of these quasars are radio sources at some level we should also
consider the possibility that the X-ray emission originates, at least
partially, in a jet.

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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: stat
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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: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: math-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas