Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: GRB 090423: Marking the Death of a Massive Star at z=8.2   GRB 090423 is the new high-z record holder of Gamma-ray bursts (GRBs) with z~
8.2. We present a detailed analysis of both the spectral and temporal features
of GRB 090423 observed with Swift/BAT and Fermi/GBM. We find that the T90
observed with BAT in the 15-150 keV band is 13.2 s, corresponding to ~ 1.4 s at
z=8.2. It once again gives rise to an issue whether the progenitors of high-z
GRBs are massive stars or mergers since the discovery of GRB 080913 at z=6.7.
In comparison with T90 distribution in the burst frame of current
redshift-known GRB sample, we find that it is marginally grouped into the long
group (Type II GRBs). The spectrum observed with both BAT and GBM is well
fitted by a power-law with exponential cutoff, which yields an Ep=50.4+/-7.0
keV. The event well satisfies the Amati-relation for the Type II GRBs within
their 3 siggma uncertainty range. Our results indicate that this event would be
produced by the death of a massive star. Based on the Amati-relation, we derive
its distance modulus, which follows the Hubble diagram of the concordance
cosmology model at a redshift of ~8.2.

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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: cs