Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Consistency with synchrotron emission in the bright GRB 160625B observed
  by Fermi   We present time resolved spectral analysis of prompt emission from GRB
160625B, one of the brightest bursts ever detected by Fermi in its nine years
of operations. Standard empirical functions fail to provide an acceptable fit
to the GBM spectral data, which instead require the addition of a low-energy
break to the fitting function. We introduce a new fitting function, called
2SBPL, consisting of three smoothly connected power laws. Fitting this model to
the data, the goodness of the fits significantly improves and the spectral
parameters are well constrained. We also test a spectral model that combines
non-thermal and thermal (black body) components, but find that the 2SBPL model
is systematically favoured. The spectral evolution shows that the spectral
break is located around $E_{\rm break}\sim$ 100 keV, while the usual $\nu
F_{\nu}$ peak energy feature $E_{\rm peak}$ evolves in the 0.5-6 MeV energy
range. The slopes below and above $E_{\rm break}$ are consistent with the
values -0.67 and -1.5, respectively, expected from synchrotron emission
produced by a relativistic electron population with a low energy cut-off. If
$E_{\rm break}$ is interpreted as the synchrotron cooling frequency, the
implied magnetic field in the emitting region is $\sim$ 10 Gauss, i.e. orders
of magnitudes smaller than the value expected for a dissipation region located
at $\sim 10^{13-14}$ cm from the central engine. The low ratio between $E_{\rm
peak}$ and $E_{\rm break}$ implies that the radiative cooling is incomplete,
contrary to what is expected in strongly magnetized and compact emitting
regions.

34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
2
The categories of this paper are: math