Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Fraction of Gamma-ray Bursts with an Observed Photospheric Emission
  Episode   There is no complete description of the emission physics during the prompt
phase in gamma-ray bursts. Spectral analyses, however, indicate that many
spectra are narrower than what is expected for non-thermal emission models.
Here, we reanalyse the sample of 37 bursts in \citet{Yu2019}, by fitting the
narrowest time-resolved spectrum in each burst. We perform model comparison
between a photospheric and a synchrotron emission model based on Bayesian
evidence. We choose to compare the shape of the narrowest expected spectra:
emission from the photosphere in a non-dissipative flow and slow-cooled
synchrotron emission from a narrow electron distribution. We find that the
photospheric spectral shape is preferred by $54 \pm 8 \%$ of the spectra
(20/37), while $38 \pm 8 \%$ of the spectra (14/37) prefer the synchrotron
spectral shape; three spectra are inconclusive. We hence conclude that GRB
spectra are indeed very narrow and that more than half of the bursts have a
photospheric emission episode. We also find that a third of all analysed
spectra, not only prefer, but are also compatible with a non-dissipative
photosphere, confirming previous similar findings.
  Furthermore, we notice that the spectra, that prefer the photospheric model,
all have a low-energy power-law indices $\alpha > -0.5$. This means that
$\alpha$ is a good estimator of which model is preferred by the data.
  Finally, we argue that the spectra which statistically prefer the synchrotron
model, could equally well be caused by subphotospheric dissipation. If that is
the case, photospheric emission during the early, prompt phase would be even
more dominant.

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The categories of this paper are: cs
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin