Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The luminosity evolution over the EQuiTemporal Surfaces in the prompt
  emission of Gamma-Ray Bursts   Due to the ultrarelativistic velocity of the expanding "fireshell" (Lorentz
gamma factor \gamma \sim 10^2 - 10^3), photons emitted at the same time from
the fireshell surface do not reach the observer at the same arrival time. In
interpreting Gamma-Ray Bursts (GRBs) it is crucial to determine the properties
of the EQuiTemporal Surfaces (EQTSs): the locus of points which are source of
radiation reaching the observer at the same arrival time. In the current
literature this analysis is performed only in the latest phases of the
afterglow. Here we study the distribution of the GRB bolometric luminosity over
the EQTSs, with special attention to the prompt emission phase. We analyze as
well the temporal evolution of the EQTS apparent size in the sky. We use the
analytic solutions of the equations of motion of the fireshell and the
corresponding analytic expressions of the EQTSs which have been presented in
recent works and which are valid for both the fully radiative and the adiabatic
dynamics. We find the novel result that at the beginning of the prompt emission
the most luminous regions of the EQTSs are the ones closest to the line of
sight. On the contrary, in the late prompt emission and in the early afterglow
phases the most luminous EQTS regions are the ones closest to the boundary of
the visible region. This transition in the emitting region may lead to specific
observational signatures, i.e. an anomalous spectral evolution, in the rising
part or at the peak of the prompt emission. We find as well an expression for
the apparent radius of the EQTS in the sky, valid in both the fully radiative
and the adiabatic regimes. Such considerations are essential for the
theoretical interpretation of the prompt emission phase of GRBs.

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The categories of this paper are: hep-ex
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The categories of this paper are: hep-th
18
The categories of this paper are: econ
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas