Young Radio Supernovae
Introduction
Publications and Simulations
Simulated Radio Images and Light Curves of SN 1993J -
Dwarkadas, Vikram V., Mioduszewski, Amy J., Ball, Lewis, to be published in the proccedings of IAU Colloquium 192, "SUPERNOVAE (10 years of SN1993J)", edited by J.M. Marcaide and K.W. Weiler, Springer Verlag 2004
- Abstract :
We present calculations of the radio images and
light curves from supernovae, based on high-resolution numerical
simulations of the hydrodynamics and radiation transfer in a
spherically symmetric medium. As a specific example we model the
emission from SN1993J. This supernova does not appear to be expanding
in a self-similar fashion, and cannot be adequately fitted with the
often-used analytic mini-shell model. We present a good fit to the
radio evolution at a single frequency. Both free-free absorption and
synchrotron self-absorption are needed to fit the light curve at early
times, and a circumstellar density profile of $\rho \sim r ^{-1.7}$
provides the best fit to the later data. Comparisons of VLBI images of
SN1993J with synthetic model images suggest that internal free-free
absorption completely obscures emission at 8.4~GHz passing through the
center of the supernova for the first few tens of years after
explosion
Simulated Radio Images and Light Curves of Young Supernovae -
Mioduszewski, Amy J.; Dwarkadas, Vikram V.; Ball, Lewis, ApJ, 562, 869
- Abstract:
We present calculations of the radio emission from supernovae based on
high-resolution simulations of the hydrodynamics and radiation
transfer, using simple energy density relations that link the
properties of the radiating electrons and the magnetic field to the
hydrodynamics. As a specific example we model the emission from SN
1993J, which cannot be adequately fitted with the often-used analytic
minishell model, and present a good fit to the radio evolution at a
single frequency. Both free-free absorption and synchrotron
self-absorption are needed to fit the light curve at early times, and
a circumstellar density profile of r^{-1.7} provides the best fit to
the later data. We show that the interaction of density structures in
the ejecta with the reverse supernova shock may produce features in
the radio light curves such as have been observed. We discuss the use
of high-resolution radio images of supernovae to distinguish between
different absorption mechanisms and determine the origin of specific
light curve features. Comparisons of VLBI images of SN 1993J with
synthetic model images suggest that internal free-free absorption
completely obscures emission at 8.4 GHz passing through the center of
the supernova for the first few tens of years after explosion. We
predict that at 8.4 GHz the internal free-free absorption is currently
declining, and that over the next ~40 yr the surface brightness of the
center of the source should increase relative to the bright ring of
emission seen in VLBI images. Similar absorption in a nearby supernova
would make the detection of a radio pulsar at 1 GHz impossible for
~150 yr after explosion.
Simulations: Here's an MPEG simulation
showing the evolution of the radio supernova with time in the
simulations. The upper frame containes the simulated images, and
the lower frame the flux density profile from the supernova. At early
times, the SN is dominated by synchrotron self-absorption, and the
flux profile is flat over the entire surface. But once the SN becomes
optically thin the radio emission peaks in the thin shell between the
inner and outer shocks. The simulations shows that the width of the
radio emission region grows with time, as expected. These simulations
compare quite well with the observations.(Please note that the
scale on the image is inverted. Red is actually the maximum flux.)
Here's the same simulation in GIF Format
You can compare these simulated images to the observed ones. Norbert
Bartel and his group have some fascinating VLBI observations of
1993J, shown here.
The acceleration and Transport of Test Particles
in Hydrodynamical Simulations - P. Duffy, V.V. Dwarkadas,
L. Ball, Proccedings of the Intl Cosmic Ray Conference, 2001
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Vikram
Dwarkadas - vikram@flash.uchicago.edu
