Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Behind the dust curtain: the spectacular case of GRB 160623A   We report on the X-ray dust-scattering features observed around the afterglow
of the gamma ray burst GRB 160623A. With an XMM-Newton observation carried out
~2 days after the burst, we found evidence of at least six rings, with angular
size expanding between ~2 and 9 arcmin, as expected for X-ray scattering of the
prompt GRB emission by dust clouds in our Galaxy. From the expansion rate of
the rings, we measured the distances of the dust layers with extraordinary
precision: 528.1 +\- 1.2 pc, 679.2 +\- 1.9 pc, 789.0 +\- 2.8 pc, 952 +\- 5 pc,
1539 +\- 20 pc and 5079 +\- 64 pc. A spectral analysis of the ring spectra,
based on an appropriate dust-scattering model (BARE-GR-B from Zubko et al.
2004}) and the estimated burst fluence, allowed us to derive the column density
of the individual dust layers, which are in the range 7x10^20-1.5x10^22 cm^-2.
The farthest dust-layer (i.e. the one responsible for the smallest ring) is
also the one with the lowest column density and it is possibly very extended,
indicating a diffuse dust region. The properties derived for the six
dust-layers (distance, thickness, and optical depth) are generally in good
agreement with independent information on the reddening along this line of
sight and on the distribution of molecular and atomic gas.

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The categories of this paper are: cond-mat
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The categories of this paper are: mtrl-th
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-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: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: funct-an