Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A high-rate foreground of sub-second flares from geosynchronous
  satellites   The Weizmann Fast Astronomical Survey Telescope (W-FAST) is a 55cm optical
survey telescope with a high cadence (25Hz) monitoring of the sky over a wide
field of view (~7deg^2). The high frame rate allows detection of sub-second
transients over multiple images. We present a sample of ~0.1--0.3s duration
flares detected in an un-targeted survey for such transients. We show that
most, if not all of them, are glints of sunlight reflected off geosynchronous
and graveyard orbit satellites. The flares we detect have a typical magnitude
of 9--11, which translates to ~14--16th magnitude if diluted by a 30s exposure
time. We estimate the rate of events brighter than ~11mag to be on the order of
30--40 events per day per deg^2, for declinations between -20 and +10^\circ,
not including the declination corresponding to the geostationary belt directly
above the equator, where the rate can be higher. We show that such glints are
common in large area surveys (e.g., ZTF and LSST), and that some of them have a
point-like appearance, confounding searches for fast transients such as Fast
Radio Burst counterparts and Gamma-ray bursts. By observing in the direction of
the Earth's shadow we are able to put an upper limit on the rate of fast
astrophysical transients of 0.052deg^{-2}day^{-1} (95\% confidence limit) for
events brighter than 11mag. We also suggest that the single image, high
declination flare observed in coincidence with the GN-z11 galaxy and assumed to
be a Gamma-ray burst, is also consistent with such a satellite glint.

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The categories of this paper are: nucl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: q-bio
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: physics
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an