Ascertaining the Core Collapse Supernova Mechanism:

1. Ascertaining the Core Collapse Supernova Mechanism: Requirements, the State of the Art, and Recent Surprises Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

2. Core Collapse Supernova Paradigm Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

3. Requirements Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

4. Anatomy of a Supernova Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

5. Newtonian versus GR A comparison of key radii in a Newtonian versus a general relativistic model (25 Solar Masses): Bruenn, DeNisco, and Mezzacappa (2001) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

6. Approach 3D Models Sophisticated Transport With and Without Rotation With and Without B Fields Newtonian, GR Increasing Complexity, Increasing Realism 2D Models Sophisticated Transport With and Without Rotation With and Without B Fields Newtonian, GR Increasing Complexity, Increasing Realism 1D Models Sophisticated Transport No Turbulence, No Rotation No B Fields Newtonian, GR …also with different weak interactions and EOS. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

7. Radiatively-Driven Phenomenon Neutrino heating depends on neutrino luminosities, spectra, and angular distributions. • Neutrino heating is sensitive to all three. • Must compute neutrino distributions: “MEMA” “ME” “Gray” Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

8. The Case for Accurate Neutrino Transport • With the exception of Wilson’s models, no models with complete multienergy transport explode. • Bruenn (1993) • Wilson and Mayle (1993) • Swesty et al. (1994) • Rampp and Janka (2000, 2002) • Bruenn, DeNisco, and Mezzacappa (2001) • Mezzacappa et al. (2001) • Liebendoerfer et al. (2001, 2005) • Thompson, Burrows, and Pinto (2003) • Mezzacappa et al. (1998) • Buras et al. (2003, 2005) Wilson’s models invoke neutron fingers. Without them, his models do not explode either. • Existence of neutronfingers is unlikely. • Bruenn and Dineva (1996) • Bruenn, Raley, and Mezzacappa (2004) 1D 2D Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

9. The Current State of the Art Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

10. Completed: Spherical Models with Boltzmann Transport Newtonian General Relativistic Mezzacappa et al. (2001) Liebendoerfer et al. (2001) Key Question: Can core collapse supernovae be powered by neutrino heating alone? • Other Roles: • Help interpret 2D and 3D models. • Explore impact of new weak interaction and EOS physics. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

11. Completed: 2D Models with RbR Neutrino Transport “Ray-by-Ray” Approximation “ME” VEF See also Buras et al. (2005). Buras et al. (2003) Buras et al. (2003) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

12. A Marginal Case • Weak explosion of 11 Solar mass progenitor. • Same physics set as Buras et al. (2003). • 180 degree polar grid. Janka et al. astro-ph/0401461 Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

13. Ongoing: 2D Simulations with 2D MGFLD Transport “ME” • Have run for only a few tens of ms after bounce. • Too early to assess final outcome. • Development of PNS instabilities apparent. Swesty and Myra (2005) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

14. Swesty and Myra (2005) Liebendoerfer et al. (2001) Fryer and Warren (2004) Buras et al. (2003) Herant et al. (1994) No B Fields Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

15. The Role of Magnetic Fields • Stellar Core Magnetic Field Amplification • (Wheeler, Meier, and Wilson 2002; Akiyama et al. 2003) • Compression • Wrapping • Dynamo • Shear (MRI) Key Questions: Are the core magnetic fields significantly amplified? Will they collimate and drive outflows? Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

16. LeBlanc and Wilson (1970), Ap.J.161, 541-551 Early Studies Symbalisty (1984), Ap.J.285, 729-746. • Jet-Like Explosion Initiated • along z-Axis (See Next Slide) • Symbalisty concluded: • required • rotation rates, • magnetic field strengths • too large. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

17. Recent Studies • Takiwaki et al. (2004) • Yamada and Sawai (2005) • Sawai, Kotake, and Yamada (2005) • Outcomes (explosion energy, collimation, …) depend on • initial field configuration, • - poloidal vs. toroidal • - uniform vs. concentrated • - strength • amount of rotation. • Conclusion • Rotation with strong fields lead to collimated explosions. • Mixed results on role of weak fields. • Mixed results on role of MRI. Sawai et al. (2005) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

18. Recent Surprises Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

19. Stationary Accretion Shock Instability (SASI) • Supernova shock wave will become unstable. • Instability will 1. help drive explosion, 2. lead to gross asphericities. New ingredient in the explosion mechanism. • Confirmed by: • Scheck et al. 2004 • Janka et al. 2005 • Ohnishi et al. 2006 • Burrows et al. 2006 Buras et al. (2003) Physics Livne et al. (2004) Physics Parameterized neutrino heating/cooling. Blondin, Mezzacappa, and DeMarino (2003) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

20. SASI: An Acoustic Phenomenon Blondin and Mezzacappa (2005a) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

21. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

22. Mechanism for Generating Polarization? Blondin, Mezzacappa, and DeMarino (2003) SASI induced flow is remarkably self similar, with an aspect ratio ~2 that is consistent with supernova spectropolarimetry data. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

23. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

24. Anatomy of a Mach Reflection Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

25. Mechanism for Generating Neutron Star Spin? SASI-Induced Rotational Flow • Implications for: • B-field amplification. • Association with progenitor spin. Blondin and Mezzacappa (2005b) Deduced NS period from deposited angular momentum: 50 ms! Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

26. Other Ideas on Supernova Acoustics • Will PNS modes couple acoustically to the postshock • region to help drive explosions? • Burrows et al. (2006) assume a coupling. • How much of what’s happening is the result of the SASI? • Need numerical experiments without shock • outer boundary to determine energy/momentum • deposition from PNS acoustic coupling. • How much of what’s happening is the result of neutrino • transport approximations? • Key pieces neglected in Burrows et al. (2006). • Impact initial conditions postbounce, spectra. • For a 15 Solar mass progenitor, do not corroborate the • Burrows et al. (2006) result. • Bruenn et al. (2006) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

27. Initial shock location/strength depend on amount of electron capture on nuclei (and protons) during stellar core collapse. Electron capture on stellar core nuclei dominated by Gamow-Teller resonance transitions in fp and gds shells, which requires knowledge of their structure. Nuclear “island” rapidly moves away from current shell model state of the art. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

28. Comparison of Stellar Collapse with IPM and "Hybrid" Models Hix et al. (2003) Change in core profiles. Change in shock formation mass. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

29. Equation of State • Issues: • Energy/Particle • Inhomogeneous Matter • Nuclei and Nuclear Matter • 1D vs. 3D Nuclei Precise form of nucleon interaction is unknown. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

30. Computing E/A: Three Approaches • “Semi-Empirical” • Polynomial expansion about infinite symmetric nuclear matter at saturation. • “Phenomenological” • Nucleon interaction potential fit to nuclear matter and nuclei (e.g., Skyrme). • “Realistic” • Nucleon interaction potential fit to free nucleon scattering data. Fundamentally different approaches allow us to explore the sensitivities. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

31. Comparison of Stellar Collapse with Different EOS Semi-Empirical, Spherical Nuclei • Lattimer-Swesty (Semi-Empirical) • Hillebrandt and Wolff (Nonrelativistic Mean Field) • Shen et al. (Relativistic Mean Field) Phenomenological, Spherical Nuclei Baird et al. (2006) Janka et al. (2004) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

32. Transition from nuclei to nuclear matter occurs through a “pasta” phase. Nuclei Lasagna Bubbles Spaghetti Anti-Spaghetti Anti-Lasagna Ravenhall, Pethick, and Wilson (1983), Phys. Rev. Lett. 150, 2006. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

33. Early Results from 3D Hartree-Fock EOS at Finite T “Phenomenological” (Skyrme), 3D Newton and Stone (2005) T=0: Magierski and Heenen, PRC 65, 045804 (2002) • New challenge: compute neutrino opacities for these extended structures. • Horowitz et al. PRC 70, 065806 (2004) Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

34. Conclusions Explosions cannot be powered by neutrino heating alone. • What impact will neutrino mixing have? • Will there be dramatic changes in the weak interaction or EOS physics? Recent simulations have uncovered a new ingredient in supernova theory. • Discovery through computation is alive and well. 2D and 3D are not the same! Much work to be done to include all 7 major model components in 3D. Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station

35. Terascale Supernova Initiative www.tsi-scidac.org • ~ 12 Institutions • ~ 18 Lead Investigators • ~ 36 Researchers • Multidisciplinary Effort • Astrophysicists • Nuclear Physicists • Applied Mathematicians • Computer Scientists Anthony Mezzacappa (ORNL) Mitchell Symposium, College Station