Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The dependence of gamma-ray burst X-ray column densities on the model
  for Galactic hydrogen   We study the X-ray absorption of a complete sample of 99 bright Swift
gamma-ray bursts. Over the last few years, a strong correlation between the
intrinsic X-ray absorbing column density (N_H(z)) and the redshift was found.
This absorption excess in high-z GRBs is now thought to be due to the
overlooked contribution of the absorption along the intergalactic medium, by
means of both intervening objects and the diffuse warm-hot intergalactic medium
along the line of sight. In this work we neglect the absorption along the IGM,
because our purpose is to study the eventual effect of a radical change in the
Galactic absorption model on the N_H(z) distribution. Therefore, we derive the
intrinsic absorbing column densities using two different Galactic absorption
models, the Leiden Argentine Bonn HI survey and the more recent model including
molecular hydrogen. We find that, if on the one hand the new Galactic model
considerably affects the single column density values, on the other hand there
is no drastic change in the distribution as a whole. It becomes clear that the
contribution of Galactic column densities alone, no matter how improved, is not
sufficient to change the observed general trend and it has to be considered as
a second-order correction. The cosmological increase of N_H(z) as a function of
redshift persists and, in order to explain the observed distribution, it is
necessary to include the contribution of both the diffuse intergalactic medium
and the intervening systems along the line of sight of the GRBs.

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The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: solv-int