John M. Blondin

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Discovering the Complexity of Supernovae through
3D Simulations
John M. Blondin NC State University
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We begin our story in 1572
On the 11th day of November in the evening
after sunset, I was contemplating the stars in a
clear sky. I noticed that a new and unusual
star, surpassing the other stars in brilliancy,
was shining almost directly above my head.
-- Tycho Brahe
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Again in 1604
Johannes Kepler observed a stella nova that
became as bright as Jupiter, but faded away after
a couple months.
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For 400 years there has not been a supernova in
our Galaxy we are still waiting!
But, in a nearby galaxy not long ago (February
1987)
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We can learn even more by looking at what is left
hundreds of years later.
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Remnants of Supernova Explosions
Relic Blastwave
Spinning Neutron Star
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The iron core contains about 3 times the mass of
our Sun, but it is roughly the size of our Earth.
This iron core collapses under its own weight
until it is small enough to fit inside Puget
Sound.
At this point the core is as dense as the nucleus
of an atom and it cannot compress any further.
The rest of the star bounces off this hard core
and explodes off into space???
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It all starts with core collapse
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The Supernova story has a long history of
computational physics

• 1966 Colgate and White
• Neutrino-Driven prompt explosion
• 1985 Bethe and Wilson
• Shock reheating via neutrino energy
  deposition
• 1992 Herant, Benz, and Colgate
• Convective instability above
  neutrino-sphere

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Anatomy of a Core-Collapse Supernova
The last decade has seen a great deal of interest
in multidimensional effects
Convection with the proto-neutron
star Neutrino-driven convection below the stalled
shock Instability of the stalled shock
All of these may operate together!
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First generation of 2D SN models hinted at a
low-order asymmetry in the shock wave at late
times (100s of msec after bounce).
Burrows, Hayes Fryxell 1995
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REU Students, Summer 2000
Christine DeMarino Brett Unks Dana Paquin
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To investigate the dynamics of the stalled
supernova shock, we consider an idealized problem
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In One Dimension
Analytical Houck Chevalier (1992) presented a
linear stability
analysis. Numerical Blondin et al. (2003)
perturb SAS and watch the
evolution.
Pressure Perturbation
Radius
Time -gt
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SN Code Verification
Houck and Chevalier 1992 Blondin and Mezzacappa
2005
This post-bounce model provides an opportunity to
verify supernova codes against the results of a
linear perturbation analysis.
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Spherical Accretion Shock Instability
Blondin, Mezzacappa, DeMarino 2003, ApJ, 584, 971
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The SASI is a global acoustic mode
The spherical accretion shock acts as an acoustic
cavity, with a trapped standing wave growing
exponentially with time.
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Must move to 3D!
This initial SASI discovery with axisymmetric 2D
simulations pointed to the obvious need for
models in full 3D.
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Hurdles for Large-Scale 3D
Not a problem
Simulation code Floating points Data output Data
transport Visualization and analysis
Thank you DOE
It works
Does not work
I cant see!
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First Results SASI Exists in 3D

• 3D Cartesian grid
• 100 Million zones
• 100s of processors
• 100s of GB in full run

Without interactive access to the data, this was
science in the dark!
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Science Begins with Data
Scientific discovery is done with interactive
access to data.

• Must have interactive access on a large-memory
  computer for analysis and visualization.
• Must have high bandwidth in accessing the data.
• Must have sufficient storage to hold data for
  weeks/months.

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Interactive Visualization of TB Datasets
A commodity linux cluster provides all the must
haves. Data is sliced into slabs and stored on
local disks on the cluster nodes. EnSight Gold
provides an easy visualization solution,
including remote client-server operation and
collaboration.
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SASI
A non-rotating, spherically symmetric progenitor
star can leave behind a neutron star spinning
with a period of tens of milliseconds.
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A Million Second Chandra View of Cassiopeia A
Hwang et. al. 2004
These are most likely due to jets of ejecta as
opposed to cavities in the circumstellar medium,
since we can reject simple models for the latter.
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If the progenitor star possessed an asymmetric
stellar wind (e.g., due to rotation), the
supernova remnant driven into this relic wind
would reflect the asymmetry of the wind.
Forward shock
Reverse shock
In this 2D simulation, the density in the
progenitor wind is four times denser in the
equatorial plane than at the poles.
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Never believe a jet in 2D
equator
pole
q
radius
equator
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A Jet from a Spherical Supernova
Fast Ejecta
Shocked Ejecta
Leading Shockwave