Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical Limits on Precursor Emission from Gamma-Ray Bursts with Known
  Redshift   Making use of virtual observatory data, we present the first comprehensive
sample of optical observations conducted before the explosion times of all
gamma-ray bursts (GRBs) with known redshifts. In total, the fields of 11 such
GRBs were observed by the Near-Earth Asteroid Tracking (NEAT) program from
years to hours before the bursts. Though the typical limiting magnitudes from
these observations are R~20 mag, we find no evidence for a significant
detection of a precursor. The deepest non-detection of precursor emission is
from GRB 030329, reaching down to an absolute B-band magnitude of M_B -18 mag
from 6--1500 days (restframe) before the burst. This is of comparable
brightness to supernovae, which, in some scenarios for GRB progenitors, are
predicted to pre-date a GRB on similar timescales. Since sources cannot be
localized to better than ~500 milliarcsecond (3 sigma) with current large-area
surveys, unrelated supernovae or AGN activity in GRB hosts could be mistaken
for genuine precursor emission. This possibility motivates the need for not
only deep wide-field imaging, but imaging at high spatial resolution.

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The categories of this paper are: eess
11
The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
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The categories of this paper are: stat
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn