Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The 2175 A dust feature in a Gamma Ray Burst afterglow at redshift 2.45   We present optical and near-infrared photometry of the afterglow of the long
Gamma-Ray Burst GRB 070802 at redshift 2.45 obtained with the ESO/MPI 2.2 m
telescope equipped with the multi-channel imager GROND. Follow-up observations
in g'r'i'z' and JHK_S bands started ~17 min and extended up to 28 h post burst.
We find an increase in brightness of the afterglow at early times, which can be
explained by the superposition of reverse and forward shock (FS) emission or
the onset of the afterglow FS. Additionally, we detect a strong broad-band
absorption feature in the i' band, which we interpret as extinction from the
redshifted 2175 A bump in the GRB host galaxy. This is one of the first and
clearest detections of the 2175 A feature at high redshift. It is strong
evidence for a carbon rich environment, indicating that Milky Way or Large
Magellanic Cloud like dust was already formed in substantial amounts in a
galaxy at z=2.45.

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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
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The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an