John M. Blondin NC State University

AAS/AAPT January 9, 2007

John M. BlondinNC State University

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Discovering the Complexity of Supernovae through 3D

Simulations




January 9, 2007AAS/AAPT

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


Again in 1604…

Johannes Kepler observed a “stella nova” that became asbright as Jupiter, but faded away after a couple months.


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)…


We can learn even more by looking at what is left hundreds of years later.


Remnants of Supernova Explosions

Relic Blastwave Spinning Neutron Star


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???


It all starts with core collapse…


• 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

The Supernova story has a long history of computational physics…


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!


First generation of 2D SN models hinted ata low-order asymmetry in the shock waveat late times (100’s of msec after bounce).

Burrows, Hayes & Fryxell 1995


REU Students, Summer 2000

Christine DeMarinoBrett UnksDana Paquin




To investigate the dynamics of the stalled supernova shock,we consider an idealized problem:


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

Time ->

Rad

ius


SN Code Verification

This post-bounce model provides an opportunity to verify supernova codes against the results of a linear perturbation analysis.

Houck and Chevalier 1992Blondin and Mezzacappa 2005


Spherical Accretion Shock Instability

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Blondin, Mezzacappa, DeMarino 2003, ApJ, 584, 971


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.





This initial SASI discovery with axisymmetric 2D simulations pointed to the obvious need for models in full 3D.

Must move to 3D!


Hurdles for Large-Scale 3D

Simulation code

Floating points

Data output

Data transport

Visualization and analysis

Not a problem

Thank you DOE

It works

Does not work

I can’t see!


First Results: SASI Exists in 3D



Without interactive access to the data, this was science in the dark!

• 3D Cartesian grid

• 100 Million zones

• 100’s of processors

• 100’s of GB in full run


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.

CrayX1

Billion-cellsimulation in 30 hoursgenerates4 terabytes

Visualizationplatform

Sharedfile

system


Interactive Visualization of TB Datasets

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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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A non-rotating, spherically symmetric progenitor star can leave behind a neutron star spinning with a period of tens of milliseconds.

SASI


A Million Second Chandra View of Cassiopeia A

“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.”

Hwang et. al. 2004


Reverse shock

Forward shock

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.

In this 2D simulation, the density in the progenitor wind is four times denser in the equatorial plane than at the poles.





equator

equator

pole

radius

Never believe a jet in 2D…





Leading Shockwave

FastEjectaShocked

Ejecta

A “Jet” from a Spherical Supernova

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