The Deflagration Phase of Type Ia SNe

Transcription

1 The Center for Astrophysical Thermonuclear Flashes The Deflagration Phase of Type Ia SNe Alan Calder ASC FLASH Center Type Ia Supernova Team Type Ia Supernovae and Cosmology August 5, 2004 An Advanced Simulation and Computing (ASC) Academic Strategic Alliances Program (ASAP) Center at

2 Evolution Towards SN Ia Light curve free expansion of envelope multi-group (non-lte) radiation transport Accretion stellar evolution code with accretion/binary evolution code Mark A. Garlick >10 8 yr P. Garnavich/CfA ~ seconds Smoldering subsonic convection in core of white dwarf low Mach number flow solver conductive heat transport ~ 1000 yr Flame initial deflagration DDT or expansion/recollapse FLASH (compressible module) with subgrid model or front-tracking conductive heat transport

3 Physics of Type Ia Supernovae Progenitor model EOS for degenerate matter Self-gravity Nuclear Energetics: 12 C+ 12 C; burn to NSQE; burn to NSE Flame model (width/radius < 10-9 ) ν s energy loss, Y e (neutronization) Complete models would include: Realistic progenitor models Magnetic fields Rotation

4 Deflagration Model: Centered Ignition Gamezo et al. (2003)

5 Gamezo et al and Reinecke et al. 2002

6 Deflagration Models: Flame Front Morphology Gamezo et al. (2002) Reinecke et al. (2002) FLASH (2004)

7 Deflagration Models: Incomplete Burning Khokhlov (2001) Energy of explosion is too small Significant mass of unburned C+O No composition stratification: complete mixing of Ni, Si, C+O throughout the star

8 3-D Delayed Detonation Model Angle-averaged chemical composition Ni C/O Si 3-D pure deflagration Mg 3-D deflagration followed by detonation Gamezo et al. (2003)

9 State-of-the-Art in Numerical Modeling grid group flame dx [km] domain ignition E [10 51 erg] remarks grid (PPM) cellbased AMR Khokhlov, Gamezo, Oran (NRL) thick, ADR 2.5 octant single extensive flame model study Def/Det Nonuniform Reinecke, Hillebrandt, Niemeyer, Roepke (DE) thin, level-set 5 octant whole star multiple 0.5+ light curve is bit too slow particles SPH Monte- Carlo Garcia-Senz, Bravo (ES)? 20 (?) full multiple 0.2 preliminary

10 The FLASH Code Shortly: Relativistic accretion onto NS Flame-vortex interactions Compressed turbulence Type Ia Supernova The FLASH code Gravitational collapse/jeans instability 1. Parallel, adaptive-mesh simulation code Wave breaking on white dwarfs 2. Designed for compressible reactive flows 3. Newly-implemented flame model 4. Includes self-gravity 6. Scales and performs well- suitable for 3-d Laser-driven shock instabilities Nova outbursts on white dwarfs Rayleigh-Taylor instability 7. Is available on the web: Helium burning on neutron stars Magnetic Rayleigh-Taylor Cellular detonation Intracluster interactions Orszag/Tang MHD vortex Richtmyer-Meshkov instability

11 Flame Model Implemented in Flash Thick flame based on an advection-reaction-diffusion equation model (Khokhlov 1995) = 4 zones Flame speed is input parameter to the model Input flame speed is the maximum of the laminar or the turbulent model speed, S = max(s lam,s sub ) S lam from Timmes and Woosley (1992) S sub from Khokhlov (1995) Self-regulating property of the model allows it to work!

12 Initial model must hold HSE long enough 1-d model interpolated onto FLASH mesh Damping removes kinetic energy to quiet the model Stable Initial Cold WD Model log(total velocity) 10 5 cm/s 10 8 cm/s

13 2-D FLASH Simulation: Central Ignition

14 Deflagration Model: Off-Center Ignition Niemeyer, Hillebrandt, & Woosley (1996)

15 Off-Center Deflagration Simulation Entire 3-d star Effective resolution of grid: Resolution: 1.6 km (1 mile!) 50 km radius ignition region offset by 12 km

16 Off-Center Deflagration Simulation entire white dwarf in 3-D ignition region 50 km radius offset 12 km from the center

17 Off-Center Deflagration Simulation

18 Off-Center Deflagration Simulation Temperature plots showing the evolution of the supersonically rising bubble

19 Off-Center Evolution: Expanding Ash Bubble

20 Off-Center Model Evolution evolution of the flame surface; r ball = 25 km t = 0.40 s t = 0.75 s

21 Off-Center Model Evolution evolution of the flame surface; r ball = 25 km t = 0.40 s t = 0.75 s

22 Global Model Characteristics

23 Results of Deflagration Simulations FLASH code is now producing 3-d calculations with high resolution. 1-, 2-, and 3-d: verified new flame module, observed symmetry in bubble geometry and multiple generations of bubbles Number of new problems/results emerged thanks to relaxing assumption of symmetry and simulating entire stars. 3-d: Off-center ignition (w. ignition region larger than displacement) produced a bubble rising to one side; burned ~ 4% of star by mass. Our study disfavors a central-ignition pure deflagration SN Ia scenario by demonstrating the sensitivity of the problem on initial conditions. The result that heavy-element-rich burned material rises to the surface may explain some peculiar Ia events (1991T, astro-ph/ ) Evolving 2-d models (cylindrical symmetry) allows for the study of bubble break-out and beyond (Following talk).

24 and that leads us to QUESTIONS AND DISCUSSION