# Presentation: 658189

## Thermonuclear Supernovae

- ASC Alliances Center for Thermonuclear Flashes, University of Chicago

- Timur Linde, Brad Gallagher, Anshu Dubey
-         Ed Brown,  Alan Calder, Alexei Khokhlov, Don Lamb, Dan Kasen,
-  Bronson Messer, Jim Truran, Natalia Vladimirova, Greg Weirs, Ju Zhang

**Thermonuclear Supernovae**
**Stellar Explosions in Three Dimensions**

**Tomek Plewa**

- Advanced Simulation and Computing (ASC)
- Academic Strategic Alliances Program (ASAP) Center
- at The University of Chicago

## What Are Type Ia SNe?

**What Are Type Ia SNe?**

- “Stella Nova” (1573), discovery chart

-  discovery by Tycho de Brahe (Nov 11, 1572)

## de Brahe’s Experience

**de Brahe’s Experience**

- J. Walker (1988)

-  mv = -4m, as bright as Venus

## Type Ia SNe Appearance

**Type Ia SNe Appearance**

- P. Nugent (LBNL)

## Tycho Supernova Remnant

**Tycho Supernova Remnant**

- SIMBAD database

-  morphology/imagining and spectra

- XMM Newton archives

## SN Ia are crucial for galactic chemical evolution.
SN Ia are also crucial for cosmology: probes allowing study of expansion and geometry  (M, ) of the Universe, nature of dark energy
Provide astrophysical setting for basic combustion problems.

**Why Do We Care?**

- SN Ia are crucial for galactic chemical evolution.
- SN Ia are also crucial for cosmology: probes allowing study of expansion and geometry  (M, ) of the Universe, nature of dark energy
- Provide astrophysical setting for basic combustion problems.

- COBE

- High-Z Supernova Search Team, HST

## Cosmological Importance

- Type Ia supernovae appear *dimmer *in the Universe with non-zero .
- Possible role of host galaxy extinction, environmental and metallicity effects (“population drift” with redshift), different evolutionary channels, intrinsic variations.

## Problem Parameters

**Channels for progenitors**
- Binary evolution
- Population synthesis
**Initial conditions **
- State of the stellar core
- Metallicity
- Rotation profile
- Magnetic fields
**Basic physics**
- Flame on intermediate scales
- Unsteadiness
- DDT
**Numerics**
- Multiphysics coupling
- Nucleosynthesis postprocessing

**Problem Parameters**

- F. Timmes

- A. Khokhlov

- Messer et al. (2004)

***INCITE 2004***

**Notes:**
Lightcurve image is a Hubble (Wide Field and Planetary Camera 2) image of SN 1997cj.

## 1960s
WD explosion proposed for Type Ia (Hoyle & Fowler)
1D detonation model (Arnett)

1970s
detonation models (several groups)
deflagration models (Nomoto)

1980s
improved 1-D deflagration models (Nomoto)
first 2-D deflagration model (Mueller & Arnett)

1990s
2-D and 3-D deflagration models, DDT (Khokhlov)
non-standard models 2-D He detonations (Livne & Arnett)
small scale flame turbulence (Niemeyer & Hillebrandt)

2000s
3-D deflagration models (NRL, MPA, Barcelona, Chicago)
3-D DDT models (NRL)

**What Has Been Done Elsewhere?**

**1960s**
- WD explosion proposed for Type Ia (Hoyle & Fowler)
- 1D detonation model (Arnett)
**1970s**
- detonation models (several groups)
- deflagration models (Nomoto)
**1980s**
- improved 1-D deflagration models (Nomoto)
- first 2-D deflagration model (Mueller & Arnett)
**1990s**
- 2-D and 3-D deflagration models, DDT (Khokhlov)
- non-standard models 2-D He detonations (Livne & Arnett)
- small scale flame turbulence (Niemeyer & Hillebrandt)
**2000s**
- 3-D deflagration models (NRL, MPA, Barcelona, Chicago)
- 3-D DDT models (NRL)

## What Do We Do?

**What Do We Do?**

-  **High-resolution integrated multi-physics models**
** **ASC allocations
-  INCITE DOE Office of Science award
-  2,700,000 SUs on NERSC seaborg
-  targeting very high resolution whole star problems
-  LANL Institutional Computing award
-  300,000 SUs on pink (2,048 proc Linux cluster)
-  targeting convergence properties at high-resolution for octants

-  **Nuclear flames**
-  review Khokhlov’s self-regulating mechanism for flame propagation
-  verify numerical implementation
-  reach down to the Gibson scale
-  understand flame surface creation/destruction mechanism
-  understand properties of the turbulent flow field

-  **Nucleosynthesis**
-  tracer particles to be used for calculation of nucleosynthetic yields
-  required for making direct links to observations
-  another multi-person effort

***INCITE 2004***

## Why Large Scale Simulations?

**Why Large Scale Simulations?**

- Alexei Khokhlov

## Self-Regulation Of The RT-Unstable Flames

**Self-Regulation Of The RT-Unstable Flames**

-  evolution of the flame surface; rball = 25 km

-             t=0.40 s

-              t=0.75 s

-      x 280%

## 8 km Resolution Central Ignition Whole Star Model

**8 km Resolution Central Ignition Whole Star Model**

***INCITE 2004***

-  Two models, 255,000 SUs and 5TB of data per model

## Ejecta Composition: Deflagration vs. DDT

**Ejecta Composition: Deflagration vs. DDT**

**Angle-averaged chemical composition**

- 3-D pure deflagration

- 3-D speculative DDT

- C/O

- Ni

- Mg

- Si

- Gamezo et al. (2003)

## Explosive Stage of Thermonuclear Supernova

**Explosive Stage of Thermonuclear Supernova**

***detonation***

***mild***
***ignition***

***deflagration***

***INCITE 2004***

***INCITE 2004***

***INCITE 2004***

- done!

- done!

- in progress

## Explosion Energy: Octants vs. Whole Star Models

**Explosion Energy: Octants vs. Whole Star Models**

***INCITE 2004***

- Octants may be nothing more than just 1/8th of the whole story.

## Is Location of The Ignition Point Important?

**Is Location of The Ignition Point Important?**

-  ignition region 50 km radius offset 12 km from the center

-  entire white dwarf in 3-D

- Calder  et al. (2004)

## What Does it Mean “Slightly Off-Center”?

**What Does it Mean “Slightly Off-Center”?**

- Off-center ignition models at 12, 20, and 35 km at 2 km resolution.

## Memory Loss of The Initial Conditions

**Memory Loss of The Initial Conditions**

- 12 km

- Variations in the offset (and initial bubble size) are unlikely to affect early evolutionary phases in any significant way.

- Off-center ignition models at 12, 20, and 35 km at 2 km resolution.

- 20 km

- 35 km

## 8 Years Between, Two Different Methods...

**8 Years Between, Two Different Methods...**

-  Niemeyer, Hillebrandt, & Woosley (1996)

-  Calder et al. (2004)

- ...and virtually the same result!

## INCITE Parameter Study of The Initial Conditions

**INCITE Parameter Study of The Initial Conditions**

-  Single ignition point, 1 km radius, 125 meters resolution

-  Impose a dipolar flow field in the core, fixed 200 km radius

-  Vary the strength of the dipole: 10, 100, and 200 km/s

-  Vary the initial distance of the bubble from the core: 0 km, 100 km

-  Rotate the dipole to minimize grid imprint

-  Evolve to 0.5 s slowly decreasing maximum resolution

-  Impose temperature limit on the energy deposition to accommodate uncertainty in the model energetics

***INCITE 2004***

-  12 models in total (about 100,000 SUs each).

## Initial Conditions: Location, Velocity Field

**Initial Conditions: Location, Velocity Field**

- r1y0v10a3030 (central, 10 km/s)

***INCITE 2004***

## Initial Conditions: Location, Velocity Field

**Initial Conditions: Location, Velocity Field**

- r1y100v100a3030 (outflowing, 100 km/s)

***INCITE 2004***

## Initial Conditions: Location, Velocity Field

- r1y100v100a3030in (inflowing, 100 km/s)

***INCITE 2004***

**Initial Conditions: Location, Velocity Field**

## Initial Conditions: Energy Generation

**Initial Conditions: Energy Generation**

- Despite strong variations in the ICs, energetic histories of all models are also similar. The system exhibits *memory loss* of initial conditions.

## Initial Conditions: Conclusion

**Initial Conditions: Conclusion**

***Based on analytic, semi-analytic, and numerical models, the most likely outcome of a mild ignition is***
***the off-center deflagration.***

## Early Post-burst Evolution in 2-D

**Early Post-burst Evolution in 2-D**

-  8 km resolution, ignition 12 km “North”, FLASH 03/2004

## Post-burst Evolution in 2-D 

**Post-burst Evolution in 2-D **

-  in long term bubble burst causes asymmetric matter distribution

## Closer Look Into Post-Burst Evolution

-  the surface flow converges at the back side of the star...

**Closer Look Into Post-Burst Evolution**

## Closer Look Into Post-Burst Evolution

-  ...collides, energy is converted into heat, density increases...

**Closer Look Into Post-Burst Evolution**

## “Gravitationally Confined Detonation”

-  ...and creates a fusion reactor -

**“****Gravitationally Confined Detonation”**

## Confined Fusion on Earth

-  magnetic (tokamaks)

**Confined Fusion on Earth**

-  inertial (lasers)

- General Atomics

## Gravitationally Confined Detonations

**Gravitationally Confined Detonations**

- Astrophys. J. Letters, 612, L37

## Spectral Signatures

**Spectral Signatures**

- Place a high-density metal-rich matter (blob from a 2-D post-breakout model) in front of the stellar ejecta (adopt standard 1-D W7).

- Contour marks XSi > 0.3.

## Spectral Signatures

**Spectral Signatures**

- Let ejecta overrun the blob. Follow to free expansion. Notice acceleration
- of the blob material and presence of significant velocity gradient.

- Contour marks XSi > 0.3.

## Spectral Signatures

**Spectral Signatures**

- Input to the spectrum calculation code (3-D Monte Carlo). Focus on the calcium line.

## GCD vs. Classic Delayed Detonation

**GCD vs. Classic Delayed Detonation**

***Unique features***
-  accommodates **imperfections in the ICs** (single-bubble deflagration)
-  **stellar pre-expansion** is driven by gravity
-  **detonation** in unconfined environment
-  the three-dimensional input to detonation is in fact **one-dimensional**
-  asymmetries resulting in specific **spectral features**

***Characteristics shared with standard DDT models***
-  mild ignition
-  deflagration followed by detonation (by the way, it is **DDT**, actually)
-  complete burn
-  pre-expansion
-  layered ejecta
-  modest degree of global asymmetry

## Summary

**Summary**

-  We have discovered that **nearly central ignition** may naturally lead to
-    **deflagration to detonation transition** due to compression and thermalization
-    of the fuel accelerated by products of the deflagration. The INCITE award will
-    allow us to study complete problem in three dimensions for the first time.

-  In our initial work in the INCITE project, we have focused on the dependence
-    of the evolution on the **initial conditions**. We have demonstrated that the
-    most likely outcome is **the off-center deflagration**.

-  We have developed **capability** for studying Type Ia supernovae using
-    integrated multi-physics large-scale computer simulations.

-  **Gravitationally Confined Detonation** model
-  displays several main characteristics of observed objects
-  fueled discussion and strengthened importance of the initial conditions
-  detonation in unconfined environment
-  conceptually detonation phase resembles that of ICF
-  natural chain of events, not by-hand, from first principles
-                    Extremely rare case in theoretical astrophysics!

***To be continued!***