941 research outputs found
A spatially resolved SSC Shock-in-Jet model
In this paper a spatially resolved, fully self-consistent SSC model is
presented. The observable spectral energy distribution (SED) evolves entirely
from a low energetic delta distribution of injected electrons by means of the
implemented microphysics of the jet. These are in particular the properties of
the shock and the ambient plasma, which can be varied along the jet axis. Hence
a large variety of scenarios can be computed, e.g. the acceleration of
particles via multiple shocks. Two acceleration processes, shock acceleration
and stochastic acceleration, are taken into account. From the resulting
electron distribution the SED is calculated taking into account synchrotron
radiation, inverse Compton scattering (full cross section) and synchrotron self
absorption. The model can explain SEDs where cooling processes are crucial. It
can verify high variability results from acausal simulations and produce
variability not only via injection of particles, but due to the presence of
multiple shocks. Furthermore a fit of the data, obtained in the 2010
multi-frequency campaign of Mrk501, is presented.Comment: 4 pages, 2 figures; appeared in the proceedings of the conference:
"High Energy Phenomena in Relativistic Outflows (HEPRO) III", held in
Barcelona, Spain, June 27th-July 1st 2011 (IJMPCS
The radio morphology of a spatially resolved SSC model
One of the main, unresolved questions about the nature of quasars is the
position of the acceleration site responsible for the highest energies. The
attempt to investigate this question in the energy regime with the highest
resolution, the radio band, has the downside that no theoretical model exists
that can connect these two regimes. The model in this work tries to shrink this
gap by extending the general synchrotron self Compton (SSC) model up to length
scales in the order of the resolution of radio observations. The resulting
spectral energy distributions (SED) show a qualitative improvement in the
representation of the radio spectrum. Furthermore the obtained emission
morphology shows similar properties to the radio structures observed in jets of
quasars. A complete and quantitative connection will however need either much
higher numerical effort or an improved methodology
Multi-band implications of external-IC flares
Very fast variability on scales of minutes is regularly observed in Blazars.
The assumption that these flares are emerging from the dominant emission zone
of the very high energy (VHE) radiation within the jet challenges current
acceleration and radiation models. In this work we use a spatially resolved and
time dependent synchrotron-self-Compton (SSC) model that includes the full time
dependence of Fermi-I acceleration. We use the (apparent) orphan -ray
flare of \textit{Mrk501} during MJD 54952 and test various flare scenarios
against the observed data. We find that a rapidly variable external radiation
field can reproduce the high energy lightcurve best. However, the effect of the
strong inverse Compton (IC) cooling on other bands and the X-ray observations
are constraining the parameters to rather extreme ranges. Then again other
scenarios would require parameters even more extreme or stronger physical
constraints on the rise and decay of the source of the variability which might
be in contradiction with constraints derived from the size of the black hole's
ergosphere.Comment: accepted for publication in Astroparticle Physic
Afterlive: A performant code for Vlasov-Hybrid simulations
A parallelized implementation of the Vlasov-Hybrid method [Nunn, 1993] is
presented. This method is a hybrid between a gridded Eulerian description and
Lagrangian meta-particles. Unlike the Particle-in-Cell method [Dawson, 1983]
which simply adds up the contribution of meta-particles, this method does a
reconstruction of the distribution function in every time step for each
species. This interpolation method combines meta-particles with different
weights in such a way that particles with large weight do not drown out
particles that represent small contributions to the phase space density. These
core properties allow the use of a much larger range of macro factors and can
thus represent a much larger dynamic range in phase space density.
The reconstructed phase space density is used to calculate momenta of the
distribution function such as the charge density . The charge density
is also used as input into a spectral solver that calculates the
self-consistent electrostatic field which is used to update the particles for
the next time-step.
Afterlive (A Fourier-based Tool in the Electrostatic limit for the Rapid
Low-noise Integration of the Vlasov Equation) is fully parallelized using MPI
and writes output using parallel HDF5. The input to the simulation is read from
a JSON description that sets the initial particle distributions as well as
domain size and discretization constraints. The implementation presented here
is intentionally limited to one spatial dimension and resolves one or three
dimensions in velocity space. Additional spatial dimensions can be added in a
straight forward way, but make runs computationally even more costly.Comment: Accepted for publication in Computer Physics Communication
Modelling the steady state spectral energy distribution of the BL-Lac Object PKS 2155-304 using a selfconsistent SSC model
In this paper we present a fully selfconsistent SSC model with particle
acceleration due to shock and stochastic acceleration (Fermi-I and
Fermi-II-Processes respectively) to model the quiescent spectral energy
distribution (SED) observed from PKS 2155. The simultaneous August/September
2008 multiwavelength data of H.E.S.S., Fermi, RXTE, SWIFT and ATOM give new
constraints to the high-energy peak in the SED concerning its curvature. We
find that, in our model, a monoenergetic injection of electrons at into the model region, which are accelerated by Fermi-I- and
Fermi-II-processes while suffering synchrotron and inverse Compton losses,
finally leads to the observed SED of PKS 2155-30.4 shown in H.E.S.S. and
Fermi-LAT collaborations (2009). In contrast to other SSC models our parameters
arise from the jet's microphysics and the spectrum is evolving selfconsistently
from diffusion and acceleration. The -factor can be interpreted as
two counterstreaming plasmas due to the motion of the blob at a bulk factor of
and opposed moving upstream electrons at moderate Lorentz factors
with an average of .Comment: 4 figure
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