Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Viscous-Dynamical Ejecta from Binary Neutron Star Merger   General-relativistic simulations of binary neutron star mergers with
viscosity reveal a new outflow mechanism operating in unequal mass binaries on
dynamical timescales and enabled by turbulent viscosity. These
"viscous-dynamical" ejecta are launched during merger due to the thermalization
of mass exchange streams between the secondary and the primary neutron star.
They are characterized by asymptotic velocities extending up to ${\sim} 0.8\,
c$, and have masses that depend on the efficiency of the viscous mechanism.
Depending on the unknown strength of the effective viscosity arising from
magnetohydrodynamics instabilities operating during merger, the overall mass of
the dynamical ejecta could be enhanced by a factor of a few and the mass of the
fast tail of the ejecta having asymptotic velocities $\geq 0.6\, c$ by up to
four orders of magnitude. The radioactive decay of the expanding
viscous-dynamical ejecta could produce bright kilonova transients with
signatures of free neutron decay in the first hour and enhanced near infrared
flux on a timescale of a few days. The synchrotron remnant produced by the
interaction between the ejecta and the interstellar medium could also be
significantly enhanced by viscosity. Such remnant could be detected in the case
of GW170817 as a rebrightening of the radio signal in the next months to years.

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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn