Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Galactic Extinction Toward GRB 970228 and Its Implications for the
  Point-Like and Extended Optical Sources   The IRAS 100 micron image of the GRB 970228 field shows that the amount of
galactic dust in this direction is substantial and varies on arcminute angular
scales. From an analysis of the observed surface density of galaxies in the
$2.6' \times 2.6'$ HST WFPC image of the GRB 970228 field, we find $A_V = 1.1
\pm 0.10$. From an analysis of the observed spectra of three stars in the GRB
970228 field, we find $A_V = 1.71^{+0.20}_{-0.40}$. This value may represent
the best estimate of the extinction in the direction of GRB 970228, since these
three stars lie only $2.7''$, $16''$, and $42''$ away from the optical
transient. If instead we combine the two results, we obtain a conservative
value $A_V = 1.3 \pm 0.2$. This value is significantly larger than the values
$A_V = 0.4 - 0.8$ used in papers to date. The value of $A_V$ that we find
implies that, if the extended source in the burst error circle is extragalactic
and therefore lies beyond the dust in our own galaxy, its optical spectrum is
very blue: its observed color $(V-I_c)_{obs} \approx 0.65^{+0.74}_{-0.94}$ is
consistent only with a starburst galaxy, an irregular galaxy at $z > 1.5$, or a
spiral galaxy at $z > 2$. On the other hand, its observed color and surface
brightness $\mu_V \approx 24.5$ arcsec$^{-2}$ are similar to those expected for
the reflected light from a dust cloud in our own galaxy, if the cloud lies in
front of most of the dust in this direction.

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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: atom-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-th
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ph