Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: XMM observations of the high-redshift quasar RXJ1028.6-0844 at z=4.276:
  soft X-ray spectral flattening   We present results from a new XMM-Newton observation of the high-redshift
quasar RXJ1028.6-0844 at a redshift of 4.276. The soft X-ray spectral
flattening, as reported by a study with ASCA previously (Yuan et al. 2000, ApJ
545, 625), is confirmed to be present, however, with reduced column density
when modelled by absorption. The inferred column density for absorption
intrinsic to the quasar is 2.1(+0.4-0.3)x10^22 (cm^-2) for cold matter, and
higher for ionised gas. The spectral flattening shows remarkable similarity
with those of two similar objects, GB1428+4217 (Worsley et al. 2004, MNRAS 350,
L67) and PMNJ0525-3343 (Worsley et al. 2004, MNRAS 350, 207). The results
improve upon those obtained from a previous short-exposure observation for
RXJ1028.6-0844 with XMM-Newton (Grupe et al. 2004, AJ 127, 1). A comparative
study of the two XMM-Newton observations reveals a change in the power-law
photon index from Gamma ~1.3 to 1.5 on timescales of about one year. A
tentative excess emission feature in the rest-frame 5-10keV band is suggested,
which is similar to that marginally suggested for GB1428+4217.

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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
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The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ph
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: nlin