Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The SDSS-XMM Quasar Sample: First Results   We have searched in the XMM-Newton public archive for quasars in the Sloan
Digital Sky Survey (SDSS) First Data Release (DR1), and found 55 lying in the
field of a XMM-Newton observation with exposure times >20 ksec (as of August,
2004). The 35 quasars which yielded good X-ray spectra span redshifts from 0.5
to 2.5. The large collecting area of XMM-Newton allows us to investigate the
dependence of the X-ray spectra of quasars on luminosity, redshift and optical
colors. We find: (1) no evolution of X-ray slope Gamma with either redshift or
luminosity; (2) no correlation between Gamma or absorbing column density and
the optical to X-ray ratio, alpha_{OX}; (4) no relation between alpha_{OX} and
optical colors. The two latter results suggest that obscuration is not the
dominant cause of the spread in X-ray slope or optical color. We find four
unusual quasars, 10% of the sample: three are absorbed (N_H>10^{22} cm^{-2}),
of which one has high luminosity (1.5x10$^{44} erg/s); the fourth has
Gamma=0.6+-0.2, far flatter than the typical value of 1.8-2.0, and a strong
emission line (EW=1.2+-$0.4 keV) which, if Fe-K, implies a redshift of ~1.4.

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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph
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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: bayes-an
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The categories of this paper are: quant-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
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The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: q-alg
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The categories of this paper are: cs