Supernova Grand Challenges on ATLAS

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Supernova Grand Challenges on ATLAS

• R. D. Hoffman
• Nuclear Theory Modeling Group
• N-DIV - LLNL

This work performed under the auspices of the
U.S. Department of Energy by Lawrence Livermore
National Laboratory under Contract
DE-AC52-07NA27344
UCRL - PRES - 401463
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CAC - Collaborators

• UCSC - S. E. Woosley D. Kasen
• LBNL (CCSE) - J. Bell, A. Almgren,
• M. Day, A. Aspden, P. Nugent
• SUNY Stony Brook - M. Zingale
• C. Malone
• LLNL (CASC) - L. Howell M. Singer

SUPRNOVA 4M CPU hrs Feb 08 3.4M
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Big Questions

• How did the Universe begin?
• How did it evolve to its present state (extent,
  composition, dynamics)?
• Where is it headed (a big crunch, long coast, a
  bounce)?
• These and other pressing questions are the
  purview of COSMOLOGY
• Current best theory The Big Bang

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Whats new? DARK ENERGY

• All agree observations at
• high red-shift are necessary.
• SNe Ia - standard candle

• Could be 2/3 of all matter and energy in the
  Universe.
• Causing the observed expansion to accelerate.
• Need to determine EOS.
• Many theories, many conflicts, little guidance.

SN 1994D
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Entering a Precision Era

• Evolutionary effects like metallicity,
  rotation, or even asymmetric explosions could
  influence our interpretation of cosmological
  parameters at high-Z.

• Use of SNe Ia as standard candles has caused a
  revolution in cosmology.
• In fact most theories are based on nearby SNe
  Ias.

Observations of higher-Z Ias suggest they have a
larger intrinsic scatter in their brightness.
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Supernova Discovery HistoryAsiago Catalog (all
supernova types)
Rvd. Evans 41 SN (81-05)
KAIT 490 SN (88-06)
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Supernova Discovery FutureRough predictions and
promises
Can we use Type Ia SNe as reliable standard
candles at the few level? Systematic error,
not statistical error, is the issue (e.g.,
luminosity evolution)
PanStarrs Dark Energy Survey JDEM Large Synoptic
Survey Telescope (LSST)
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SN Ia ProgenitorsAccreting white dwarf near the
Chandrasekhar limit
Issues with the single degenerate scenario Where
is the hydrogen? How do you make them in old (10
Gyr) systems? What about observed Super-Chandra
events? Could double white dwarf systems be the
answer?
Accretion rate 10-7 Msun / year
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MWD1.38 Msun
C/O
boom
rc3x109 g/cc
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Type Ia Supernova Light Curvespowered by the
beta decay 56Ni 56Co 56Fe
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Type Ia Width-Luminosity Relationbrighter
supernovae have broader light curves
Lp f(w)
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Type Ia Supernova Spectrum
Most Sne Ias look similar line features of
doubly ionized Mg, Si, S, Ca (intermediate Z) as
well as Fe, Co
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Time Evolution of SpectrumRecession of
photosphere reveals deeper layers
Day 35 after explosion
C/O
Si/S/Ca
Model SN1994D
56Ni
Fe
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Ma 2007
Presupernova Evolution (1000 -109
years) accreting, convective white dwarf
ignition
RWD 1800 km
Explosion (1-100 secs) turbulent nuclear
combustion / hydrodynamics
free expansion
Roepke 2007
w 10-4 cm
Light Curves / Spectra (1-100 days) radioactive
decay / radiative transfer
Kasen 2007
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The Theoretical Understanding of Type Ia
Supernovae
Pressing Questions
What are the progenitors? How and where does
ignition happen? How might the deflagration
transition into a detonation? How
do the light curves and spectra depend upon the
progenitor, its environment and the nature of the
explosion?
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low Mach number hydro codes
SNe MAESTRO
Able to take large time steps based on the fluid
velocity rather than the speed of sound in the
star. SNe designed to study the microphysics
of nuclear flames and how the flame interacts
with turbulence. Forms the basis of the sub-grid
model needed for the full star calcs. MAESTRO
incorporates background density stratification
of the star and compressibility effects due to
heat release and buoyancy. CASTRO our
compressible rad-hydro code used for late time
simulations when the low Mach number assumption
is no longer valid. Also for SNII GRBs.
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3-dimensional Time-Dependent Monte Carlo
Radiative Transfer
SEDONA Code Expanding atmosphere Realistic
opacities Three-dimensional Time-dependent Multi-w
avelength Includes spectropolarization Treats
radioactive decay and gamma-ray
transfer Iterative solution for thermal
equilibrium Non-LTE capability
Kasen et al 2006 ApJ
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2D Deflagration Model
Roepke, Kasen, Woosley
MNi 0.2 Msun EK 0.3 x 1051 ergs
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The stronger the deflagration phase ?? the more
pre-expansion ?? the lower the densities at
detonation ?? the less 56Ni produced
2D Delayed Detonation
Roepke, Kasen, Woosley
MNi 0.5 Msun EK 1.2 x 1051 ergs
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Off-center Detonation
Roepke, Kasen, Woosley
An alternative to super-chandra SNe? Howell et
al, 2006 Hillebrandt, Sim, Roepke 2007
MNi 1.0 Msun EK 1.3 x 1051 ergs
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Spectrum of Off-center Detonationexpansion
velocities depend on orientation
I-Band
Kasen (2006) ApJ
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Asymmetry and PolarizationModel polarization
spectrum at maximum lightas seen from different
viewing angles
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Transition to Detonation

• Hot ash plumes surrounded by the flame are
  buoyant. As they rise, encountering lower
  densities, shear gives rise to turbulence, which
  cascades to smaller length scales where it
  affects the motion of the flame, it thickens.
• A critical length-scale in turbulent combustion
  is the Gibson scale lGthe scale at which the
  flame can just burn away a turbulent eddy before
  it turns over

where sL is the laminar flame speed, L is the
integral scale and v'(L) is the turbulent
intensity on that scale (with assumed Kolmogorov
scaling).
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Simulating turbulence

• At around 107 g cm-3, the flame becomes thick
  enough that turbulent eddies can disrupt its
  structure before they burn away, that is, the
  flame thickness is larger than the Gibson scale.
• At this point, the burning fundamentally changes
  character and the flame is said to be in the
  distributed burning regime.
• 3-D simulations showing the distribution of
  nuclear energy generation in turbulent carbon
  fusion flames spanning

• The flamelet regime (0.3 m)2
• r 8x107 g/cc , u 0.1 sL
• Transitional stage (0.3m)2
• r 3x107 g/cc , u 1.8 sL
• The distributed regime (1.0 m)2
• r 1x107 g/cc, u 70.0 sL
• where u is an imposed turbulence level.
• Q In the distributed burning regime, can a mixed
  region of partially burned fuel and ash grow
  large enough such that it can ignite a detonation?

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Here the turbulence is dominated by the flame,
which remains fairly coherent and burns in a
similar way to a flat laminar flame. The red line
is the locus of a laminar flame at the same
density.
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Turbulent disruption of the flame leads to
thermodiffusively stable behavior expected of a
high Lewis number flame, where regions of
negative and positive curvature experience
greatly enhanced and reduced burning rates,
respectively.

Intense burning regions and local extinction are
both observed. The width of the flame is slightly
increased, but the overall burning rate remains
close to the laminar value.
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Turbulent mixing dominates over diffusive
processes shredding the flame. Its thickness is
greatly increased accompanied by a 5-fold
increase in burning rate. We are currently
generating statistics that will further refine
the subgid model for our full star studies.
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SNe Ia Highlights on ATLAS

• Code development is nearly complete on MAESTRO,
  the low Mach-number code, and CASTRO, the
  compressible radiation-hydro code. SEDONA now has
  non-LTE capability - distributed MC in progress.
  Full star 3D studies to begin in summer 08.
• The light curves and spectra of a set of 1D and
  2D models for Type Ia supernovae were calculated.
  The physical origin of the WLR has been
  determined. Significant variations in spectra and
  brightness as a function of viewing angle for
  asymmetric explosions were observed, which could
  explain the so called super-Chandrasekhar mass
  Type Ia supernovae' for a single degenerate
  progenitor.
• Turbulent nuclear combustion in the distributed
  regime has been studied analytically and
  simulated. We see the broadening of the flame by
  turbulence and have derived the necessary
  criteria for a transition to detonation.

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low Mach number hydro codes
SNe MAESTRO
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References

• Type Ia Supernovae, Woosley et al. Journal of
  Physics Conference Series \bf 78, (2007)
  012081
• The Light Curves and Spectra of Supernova
  Explosions Multi-Dimensional Time-Dependent
  Monte Carlo Radiative Transfer Calculations,
  Kasen et al. Journal of Physics Conference
  Series 78, (2007) 012037
• "Adaptive low Mach number simulations of nuclear
  flame microphysics", J. B. Bell, M. S. Day, C. A.
  Rendleman, S. E. Woosley, and M. A. Zingale, LBNL
  Report 52395, J. Comp. Phys, 195, 677-694, 2004.
• "MAESTRO A Low Mach Number Stellar Hydrodynamics
  Code", Almgren, A.S., Bell, J.B., Zingale, M.,
  Journal of Physics Conference Series 78, (2007)
  012085
• SEDONA "Time Dependent Monte Carlo Radiative
  Transfer Calculations for 3-Dimensional Supernova
  Spectra, Lightcurves, and Polarization", D.
  Kasen, R.C. Thomas, P. Nugent, astro-ph/0606111
  (2006) URL http//arxiv.org/abs/astro-ph/0606111