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Supernova Grand Challenges on ATLAS

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. CAC - Collaborators.

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Supernova Grand Challenges on ATLAS

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  1. 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

  2. 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

  3. 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

  4. What’s 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

  5. 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 Ia’s. Observations of higher-Z Ia’s suggest they have a larger intrinsic scatter in their brightness.

  6. Supernova Discovery HistoryAsiago Catalog (all supernova types) Rvd. Evans: 41 SN (81-05) KAIT: 490 SN (88-06)

  7. Supernova Factory Lick observatory SN search CfA SN group Carnegie SN project ESSENCE Supernova Legacy Survey 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)

  8. 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

  9. C/O Si/S/Ca 56Ni Fe MWD=1.38 Msun C/O boom rc=3x109 g/cc

  10. Type Ia Supernova Light Curvespowered by the beta decay: 56Ni 56Co 56Fe

  11. Type Ia Width-Luminosity Relationbrighter supernovae have broader light curves Lp = f(w)

  12. Type Ia Supernova Spectrum Most Sne Ia’s look similar: line features of doubly ionized Mg, Si, S, Ca (intermediate Z) as well as Fe, Co

  13. Day 15 after explosion Time Evolution of SpectrumRecession of photosphere reveals deeper layers Day 35 after explosion C/O Si/S/Ca Model SN1994D 56Ni Fe

  14. t = 0.0 sec t = 0.5 sec t = 1.0 sec t = 1.5 sec 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

  15. 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?

  16. 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 themicrophysics of nuclear flames and how the flame interacts with turbulence. Forms the basis of the sub-grid model needed for the full star calc’s. 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 & GRB’s.

  17. 3-dimensional Time-Dependent Monte Carlo Radiative Transfer SEDONA Code Expanding atmosphere Realistic opacities Three-dimensional Time-dependent Multi-wavelength Includes spectropolarization Treats radioactive decay and gamma-ray transfer Iterative solution for thermal equilibrium Non-LTE capability Kasen et al 2006 ApJ

  18. 2D Deflagration Model Roepke, Kasen, Woosley MNi = 0.2 Msun EK = 0.3 x 1051 ergs

  19. 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

  20. 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

  21. Spectrum of Off-center Detonationexpansion velocities depend on orientation I-Band Kasen (2006) ApJ

  22. Asymmetry and PolarizationModel polarization spectrum at maximum lightas seen from different viewing angles

  23. 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 lG—the 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 scaleand v'(L) is the turbulent intensity on that scale (with assumed Kolmogorov scaling).

  24. Simulating turbulence • 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? • 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:

  25. 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.

  26. 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.

  27. 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.

  28. 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.

  29. low Mach number hydro codes SNe & MAESTRO

  30. 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

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