Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: How to Tell a Jet from a Balloon: A Proposed Test for Beaming in Gamma
  Ray Bursts   If gamma ray bursts are highly collimated, the energy requirements of each
event may be reduced by several (~ 4-6) orders of magnitude, and the event rate
increased correspondingly. Extreme conditions in gamma ray bursters lead to
highly relativistic motions (bulk Lorentz factors Gamma > 100). This results in
strong forward beaming of the emitted radiation in the observer's rest frame.
Thus, all information on gamma ray bursts comes from those ejecta emitted in a
narrow cone (opening angle 1/Gamma) pointing towards the observer. We are at
present ignorant of whether there are ejecta outside that cone or not.
  The recent detection of longer wavelength transients following gamma ray
bursts allows an empirical test of whether gamma ray bursts are collimated jets
or spherical fireballs. The bulk Lorentz factor of the burst ejecta will
decrease with time after the event, as the ejecta sweep up the surrounding
medium. Thus, radiation from the ejecta is beamed into an ever increasing solid
angle as the burst remnant evolves. It follows that if gamma ray bursts are
highly collimated, many more optical and radio transients should be observed
without associated gamma rays than with them. Published supernova searches may
contain enough data to test the most extreme models of gamma ray beaming. We
close with a brief discussion of other possible consequences of beaming,
including its effect on the evolution of burst remnants.

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The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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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: mtrl-th
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: physics
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph