Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Subsequent Nonthermal Emission due to the Kilonova Ejecta in GW 170817   The ejected material at the binary neutron star merger GW 170817 was
confirmed as a kilonova by UV, optical, and IR observations. This event
provides a unique opportunity to investigate the particle acceleration at a
mildly relativistic shock propagating in the circumbinary medium. In this
paper, we simulate the nonthermal emission from electrons accelerated by the
shock induced by the kilonova ejecta with a time-dependent method. The initial
velocity and mass of the ejecta in the simulations are obtained from the
kilonova observations in GW 170817. If the ambient density is high enough
($\geq 10^{-2}~\mbox{cm}^{-3}$), radio, optical/IR, and X-ray signals will be
detected in a few years, though the off-axis short gamma-ray burst models,
accounting for the X-ray/radio counterpart detected at $\sim 10$ days after the
merger, implies low ambient density. We also demonstrate that the additional
low-mass ($\sim 10^{-5} M_\odot$) component with a velocity of $0.5 c$--$0.8 c$
can reproduce the early X-ray/radio counterpart. This alternative model allows
a favorably high density to detect the nonthermal emission due to the kilonova
ejecta. Even for a low ambient density such as $\sim 10^{-3}~\mbox{cm}^{-3}$,
depending on the microscopic parameters for the electron acceleration, we can
expect a growth of radio flux of $\sim 0.1$ mJy in a few years.

35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn