Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: GRB 071003: Broadband Follow-up Observations of a Very Bright Gamma-Ray
  Burst in a Galactic Halo   The optical afterglow of long-duration GRB 071003 is among the brightest yet
to be detected from any GRB, with R ~ 12 mag in KAIT observations starting 42 s
after the GRB trigger, including filtered detections during prompt emission.
However, our high S/N ratio afterglow spectrum displays only extremely weak
absorption lines at what we argue is the host redshift of z = 1.60435 - in
contrast to the three other, much stronger Mg II absorption systems observed at
lower redshifts. Together with Keck adaptive optics observations which fail to
reveal a host galaxy coincident with the burst position, our observations
suggest a halo progenitor and offer a cautionary tale about the use of Mg II
for GRB redshift determination. We present early through late-time observations
spanning the electromagnetic spectrum, constrain the connection between the
prompt emission and early variations in the light curve (we observe no
correlation), and discuss possible origins for an unusual, marked rebrightening
that occurs a few hours after the burst: likely either a late-time refreshed
shock or a wide-angle secondary jet. Analysis of the late-time afterglow is
most consistent with a wind environment, suggesting a massive star progenitor.
Together with GRB 070125, this may indicate that a small but significant
portion of star formation in the early universe occurred far outside what we
consider a normal galactic disk.

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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
31
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: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: supr-con