Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The extreme, red afterglow of GRB 060923A: Distance or dust?   Gamma-ray bursts are powerful probes of the early universe, but locating and
identifying very distant GRBs remains challenging. We report here the discovery
of the K-band afterglow of Swift GRB 060923A, imaged within the first hour
post-burst, and the faintest so far found. It was not detected in any bluer
bands to deep limits, making it a candidate very high redshift burst (z>11).
However, our later-time optical imaging and spectroscopy reveal a faint galaxy
coincident with the GRB position which, if it is the host, implies a more
moderate redshift (most likely z<2.8) and therefore that dust is the likely
cause of the very red afterglow colour. This being the case, it is one of the
few instances so far found of a GRB afterglow with high dust extinction.

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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph