Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chandra grating spectroscopy of embedded wind shock X-ray emission from
  O stars shows low plasma temperatures and significant wind absorption   We present a uniform analysis of six examples of embedded wind shock (EWS) O
star X-ray sources observed at high resolution with the Chandra grating
spectrometers. By modeling both the hot plasma emission and the continuum
absorption of the soft X-rays by the cool, partially ionized bulk of the wind
we derive the temperature distribution of the shock-heated plasma and the wind
mass-loss rate of each star. We find a similar temperature distribution for
each star's hot wind plasma, consistent with a power-law differential emission
measure, $\frac{d\log EM}{d\log T}$, with a slope a little steeper than -2, up
to temperatures of only about $10^7$ K. The wind mass-loss rates, which are
derived from the broadband X-ray absorption signatures in the spectra, are
consistent with those found from other diagnostics. The most notable conclusion
of this study is that wind absorption is a very important effect, especially at
longer wavelengths. More than 90 per cent of the X-rays between 18 and 25
Angstrom units produced by shocks in the wind of $\zeta$ Puppis are absorbed,
for example. It appears that the empirical trend of X-ray hardness with
spectral subtype among O stars is primarily an absorption effect.

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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: math
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph