Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Monte-Carlo simulations of relativistic radiation mediated shocks: II.
  photon starved regime   Radiation mediated shocks (RMS) play a key role in shaping the early emission
observed in many transients. In most cases, e.g., shock breakout in supernovae,
llGRBs and neutron star mergers, the upstream plasma is devoid of radiation,
and the photons that ultimately reach the observer are generated predominantly
inside and downstream of the shock. Predicting the observed spectrum requires
detailed calculations of the shock structure and thermodynamic state that
account properly for the shock microphysics. We present results of
self-consistent Monte-Carlo simulations of photon-starved RMS, that yield the
shock structure and emission for a broad range of shock velocities, from
sub-relativistic ($\beta_{sh} = 0.1$) to highly relativistic ($\Gamma_{sh} =
20$). Our simulations confirm that in relativistic RMS the immediate downstream
temperature is regulated by exponential pair creation, ranging from $50$ keV at
$\beta_{sh}=0.5$ to $200$ keV at $\Gamma_{sh}=20$. At lower velocities the
temperature becomes sensitive to the shock velocity, with $kT\sim 0.5$ keV at
$\beta_{sh}=0.1$. We also confirm that in relativistic shocks the opacity is
completely dominated by newly created pairs, which has important implications
for the breakout physics. We find the transition to pair dominance to occur at
$\beta_{sh}=0.5$ roughly. In all cases examined, the spectrum below the $\nu
F_\nu$ peak has been found to be substantially softer than the Planck
distribution. This has important implications for the optical emission in fast
and relativistic breakouts, and their detection. The applications to GRB 060218
and GRB 170817A are discussed.

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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
2
The categories of this paper are: math
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The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg