Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectral and timing properties of the accreting X-ray millisecond pulsar
  IGR J17498-2921   We analyze the spectral and timing properties of IGR J17498-2921 and the
characteristics of X-ray bursts to constrain the physical processes responsible
for the X-ray production in this class of sources. The broad-band average
spectrum is well-described by thermal Comptonization with an electron
temperature of kT_e ~ 50 keV, soft seed photons of kT_bb ~ 1 keV, and Thomson
optical depth \taut ~ 1 in a slab geometry. The slab area corresponds to a
black body radius of R_bb ~9 km. During the outburst, the spectrum stays
remarkably stable with plasma and soft seed photon temperatures and scattering
optical depth that are constant within the errors. This behavior has been
interpreted as indicating that the X-ray emission originates above the neutron
star (NS) surface in a hot slab (either the heated NS surface or the accretion
shock). The INTEGRAL, RXTE, and Swift data reveal the X-ray pulsation at a
period of 2.5 milliseconds up to ~65 keV. The pulsed fraction is consistent
with being constant, i.e. energy independent and has a typical value of 6-7%.
The nearly sinusoidal pulses show soft lags that seem to saturate near 10 keV
at a rather small value of ~ -60\mu s with those observed in other accreting
pulsars. The short burst profiles indicate that there is a hydrogen-poor
material at ignition, which suggests either that the accreted material is
hydrogen-deficient, or that the CNO metallicity is up to a factor of about two
times solar. However, the variation in the burst recurrence time as a function
of \dot{m} (inferred from the X-ray flux) is much smaller than predicted by
helium-ignition models.

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The categories of this paper are: hep-ph
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The categories of this paper are: stat
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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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: quant-ph