Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: XMM-Newton observations of MR Vel/RX J0925.7-4758   We report on XMM-Newton observations of the galactic supersoft X-ray source
RX J0925.7-4758. The RGS spectrum exhibits a wealth of spectral features from
iron and oxygen. XMM-Newton data confirm the finding of previous Chandra
HETGS/MEG observations that NLTE models of hot white dwarf atmospheres fail to
represent the complex spectrum. There are clear evidences for P Cygni profiles
with wind velocities of up to 2000 km/s. Small flux variations with time scales
larger than 1000s are present. The strongest power is at ~ 0.21d, a period
close to that seen in V band optical light curves. A detailed analysis of the
associated changes in the RGS and EPIC pn spectra hint at a mostly grey
mechanism suggesting a variation of the visibility of the white dwarf due to
occulting material in the accretion disk. Finally, we detect radial velocity
changes of 173 +/- 47 km/s between two RGS observations obtained half an
orbital cycle apart. The amplitude of the RGS velocity shift is consistent with
that of the optical He II 4686 and thus supports the idea that most of the He
II optical line emission arises from the accretion disk.

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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th
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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: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-ex