Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On-Axis Orphan Afterglows   In many GRB inner engine models the highly relativistic GRB jets are engulfed
by slower moving matter. This could result in different beaming for the prompt
$\gamma$-ray emission and for the lower energy afterglow. In this case we
should expect that some observer will see {\it on-axis orphan afterglows}:
X-ray, optical and radio afterglows within the initial relativistic ejecta with
no preceding GRB; The prompt $\gamma$-ray emission is pointing elsewhere. We
show that the observations of the WFC on BeppoSAX constrain with high certainty
the prompt X-ray beaming factor to be less than twice the prompt $\gamma$-ray
beaming. The results of Ariel 5 are consistent with this interpretation. The
RASS from ROTSE and HEAO-1 constrain the X-ray beaming factor at 400 and 20
minutes after the burst respectively to be comparable and certainly not much
larger than the $\gamma$-ray beaming factor. There is no direct limit on the
optical beaming. However, we show that observations of several months with
existing hardware could result in a useful limit on the optical beaming factor
of GRB afterglows.

27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: nlin