blowing up massive starsaspen08.gravity.psu.edu/program/ott_aspen_mai_2008.pdfc. d. ott @ aspen, may...

Blowing up Massive Stars

Constraining the Mechanism of Core-Collapse Supernova Explosions

with Gravitational Waves

Christian David Ott

Adam Burrows (Princeton)

Eli Livne (Jerusalem)

Luc Dessart (Princeton)

Jeremiah Murphy (Arizona)

Harald Dimmelmeier (Thessaloniki/Garching)

Hans-Thomas Janka (MPA Garching)

Andreas Marek (MPA Garching)

Ewald Müller (MPA Garching)

Ian Hawke (Southampton), Erik Schnetter (Louisiana State), Burkhard Zink (Louisiana State), Ed Seidel (LSU), Bernard Schutz (AEI)

Joint Institute for Nuclear Astrophysics Postdoctoral Fellow

Steward Observatory & Department of Astronomy, The University of Arizona [email protected]

Gravitational Waves

C. D. Ott @ Aspen, May 2008 3

• Einstein equations in linear limit: Inhomogeneous wave equations -> Gravitational Waves.

• 2 polarizations:

• Emission: GWs are of leading order quadrupole waves. Emitted by accelerated aspherical bulk-mass motions.“Weak-field”, “slow-motion” limit:

• GWs are weak and couple weakly to matter. Good: Little absorption/scattering Bad: Very difficult to observe.

• Observation: Need to measure rel. displacements < 10-20.

– Interferometers: LIGOs, LISA

– Resonant mass detectors.

LIGO Hanford2 km & 4 km interferometers

A Supernova Primer


• More exotic:– Accretion-induced collapse (AIC)

of white dwarfs to neutron stars.

– Pair-instabilty supernovae: thermonuclear; pulsational instability / disruption.

– Failed core-collapse SNe -> Collapsars.

Supernova Classes

Thermonuclear SNe Core-Collapse SNe

Evolved low-mass Stars (White Dwarfs)

Evolved massive Stars (Supergiants)

(Accretion-induced)

thermonuclear Explosion

Gravitational Collapse

-> Release of grav. Energy

None Neutron Star or Black Hole

Progenitors

Basic Mechanism

Compact Remnant

Spectroscopic Types Type Ia Type II, Ib, Ic

1 SN/sec/Universe1 SN/40 years/Milky Way1 SN Ia/5-10 SN II

Why do we care about Supernovae?

C. D. Ott @ Aspen, May 20085

• Cosmic polluters

• Cosmic standard candles.

• End points of stellar evolution.

• Dynamical impact on galaxy evolution.

• Stellar collapse: The making of neutron stars and black holes.

– Formation and co-evolution of black holes and galaxies.

– Core-collapse SN – Gamma-Ray Burst [GRB] relationship.

Source: NASA

The Core-Collapse SN Scenario• MZAMS ≥ 8—10 MSun• Nuclear fusion up to iron-group

nuclei.

• Iron core: electron degenerate, Chandrasekhar-mass object;EOS:

• Effective Chandrasekhar mass:

1.4 – 2 MSun.

• Onset of gravitational collapse when pushed over effective MCh:Photo-dissociation of nuclei and electron capture.

C. D. Ott @ Aspen, May 2008 6Betelgeuse as seen by the HST

Collapse, Bounce & Explosion• Collapse separates iron core into

homologously (vr) collapsing inner core and supersonicallycollapsing outer core.

• EOS stiffens at ρnuc:Inner core bounce, hydrodynamic bounce shock.

• Shock loses kinetic energy todissociation + neutrino losses:-> Shock stalls.

• Shock revival and SN explosionor collapse to BH (collapsar/GRB?).

• What is the mechanism of shock revival?


Explosion mechanism must tap the gravitational energy reservoir and convert the necessary

fraction into energy of the explosion.


The Essence of Core-Collapse Supernova Explosion Mechanisms

• Collapse to neutron star: 3 x 1053 erg = 300 Bethe [B] gravitational energy.

• 1051 erg = 1 B kinetic and internal energy of the ejecta. (Extreme cases: 1052 erg; “hypernova”)

• 99% of the energy is radiated as neutrinos over hundreds of seconds as the protoneutron star (PNS) cools.

• Neutrino-driven mechanism:Based on subtle imbalance between neutrino heating and cooling in postshock region.

45+ Years of Theory & Modeling


[Wilson 1985; Bethe & Wilson 1985]

• Bounce shock always stalls. Direct hydrodynamic “prompt” mechanism fails.

[Thompson et al. 2003, Rampp & Janka2002, Liebendörfer et al. 2002,2005]

[Ott

et

al. 2

00

8]

Problem: Fails to explode garden-variety massive stars in spherical symmetry.

Breaking of spherical symmetry probably key ingredient of the SN mechanism!

Standing Accretion Shock Instability


[e.g., Blondin et al. 2003,2006; Foglizzo et al. 2006, Scheck et al. 2006, 2007, Burrows et al. 2006, 2007 ]

Advective-acoustic cycle drives shock instability.

Seen in simulations byall groups!

Rapid Rotation and Nonaxisymmetric Dynamics


3D GR simulation Ott 2006, rendition by R. Kähler, Zuse Institute, Berlin

12

PNS core oscillations, Burrows et al. 2006, 2007; Ott et al. 2006

Blowing up Massive Stars: Core-Collapse SN Mechanisms


• Standard Neutrino mechanism works in 1D for lowest-mass massive stars (O-Ne-Mg cores). 2D: accretion induced collapse with rapid rotation.

• More massive progenitors: Multi-D effects probably crucial:Convection, accretion shock instabilities, rotation, MHD, PNS pulsations.

2D/3D Neutrino Mechanism

+ ν energy deposition.

+ Convection/Standing-Accretion-Shock Insta-bility (SASI) & soft EOS.-> 11.2 MSUN, 15 MSUN*Buras et al. ’06, Marek & Janka ‘07+

+ Si/O burning.[Bruenn et al. ’06, Mezzacappa et al. ‘07+

MHD-Jet Mechanism

+ Rapid Rotation+ B-field amplification:

flux compression, MRI,winding, dynamos

+ Robust, early jet-drivenexplosions (up to 10 B).*e.g., Burrows et al. ‘07, Wilson et al. ‘05,Yamada & Sawai ‘04, Mizuno et al. ‘04, Akiyama et al. ’03, ’05, Shibata et al. ‘06+

Acoustic Mechanism

+ Excitation of PNS g-modepulsations by accretion/ SASI/turbulence.

+ Damping via emission of strong sound waves that steepen to shocks.

+ Robust, late explosions.*Burrows et al. ‘06, ’07, Ott et al. ’07,but: Weinberg & Quatert ’07+

[Kitaura et al. 2006, Burrows 1987, 2007c]

*Dessart et al. ‘06, ‘08+

Modeling the Core-Collapse SN Mechanism


• Ingredients: multi-D (M)HD, GR, neutrino transport & microphysics, finite-temperature nuclear EOS, nuclear reactions.

• GR / approx. GR / Newtonian:– 3+1 ADM/BSSN, conformally flat (CFC), GR hydro.– approximate GR “potentials”, Newtonian hydro.– straight-out Newtonian.

• Neutrinos:– Boltzmann transport (3D+3D+time->7D).

– (multi-group) flux-limited diffusion ([MG]FLD).

– Leakage schemes / parametrizations.

– Multi-D transport vs. ray-by-ray approximation.

• Equation of state:– Liquid drop model, Hartree-Fock / Thomas-Fermi,

(relativistic) mean-field approximations [all tabulated].

– Polytropes & Γ-Laws.

Enrico

Hans

Albert

Ludwig

Dave Sterling Jim

Status of Multi-D Core-Collapse Supernova Simulations


Group Hydro MHD Transport Explosion Year References

MPAGarching

2D No Ray-by-Ray1D Boltzmann

Yes:ν/SASI,

1D ν-wind

2007 Marek & Janka 2007,Buras et al. 2006

LANL 2D/3D No gray FLD Yes:ν/SASI

2007 Fryer & Young 2007,Fryer & Warren 2004

ORNL 2D/3D No Ray-by-Ray1D MGFLD

Yes:ν/SASI +burning

2007 Bruenn et al. 2006,Mezzacappa et al. 2007

Stony Brook 2D No 2D MGFLD -- 2006 Swesty & Myra 2006

Basel 3D Yes Ye parametrization -- 2007 Scheidegger et al. 2007

Princeton/Arizona/

Jerusalem

2D Yes 2D MGFLD / 2D Boltzmann

Yes:acoustic, MHD,

ν-wind

2007 Burrows et al. 2006, 2007Ott et al. 2006, 2008,

Dessart et al. ‘06, ‘07, ‘08

Tokyo/Waseda

2D/3D Yes Light-Bulb(/MGFLD)

--- 2007 Iwakami et al. 2007,Ohnishi et al. 2007,Kotake et al. 2007

Newtonian & “Pseudo-Relativistic” Potential Calculations (Disclaimer: To my best knowledge no guarantee for completeness; including recently published studies only.)

Status of General-Relativistic Multi-D Core-Collapse Simulations


Group Hydro MHD Curvature EOS Neutrinos Year References

UIUC/Tokyo

2D/3D Yes BSSN Polytropic/Γ-Law

none 2007 Shibata & Sekiguchi’04,’05,’06

Shibata et al. 06

Arizona (Ott)/

Garching/LSU

2D/3D

AMR

No BSSN (3D)CFC (2D)

Shen/LSEOS

Yeparametrization

2007 Ott et al. ’07ab,Dimmelmeier et al.

’07, 08 (in prep.)

Garching/Valencia

2D Yes CFC/CFC+ Shen/LS EOS

Yeparametrization

2007 Cerda-Duran et al. ’05, ‘07

(Disclaimer: To my best knowledge no guarantee for completeness; Including recent studies only.)

• Previous/present focus of GR simulations:

– Rotating collapse & bounce -> GW emission.

– Non-axisymmetric rotational instabilities.

MHD-driven Explosions

17

[Livne et al. 2007, Burrows et al. 2007]

• VULCAN 2D R-MHD code.

• Precollapse period P0 = 2 s.

• If MRI efficient, fast postbounce amplification to 1015 G.

• Here: MRI not resolved.Initial B-fields of 1010—1012

G. 1011 G 1015 G postbounce.

• MHD-driven explosionmay be GRB precursor.


18

Acoustic Mechanism

• Late explosions.

• Very aspherical.

• Very high-entropy outflows. s up to 300 kb/baryon.

• Site for the r-process?

Remarks on the Mechanisms

C. D. Ott @ Caltech 01/2008 19

• Neutrino Mechanism:– Needs convection & SASI, so far shown to work only with (too) soft EOS.

– May not work with: rapid rotation, stiffer EOS.

• MHD Mechanism:– Requires very rapid rotation (P0 < 4 s), but most iron cores may be

rotating with P0 > 30 s.

– Precollapse magnetization probably very weak. -> Mechanism depends on efficiency of dynamical magneto-rotational instabilities / dynamos.

• Acoustic Mechanism:– Proposed by Burrows et al.

Independent confirmation difficult: Requires singularity-free numerical grid.

– Explosions occur late (t > 1 s) and are often under-energetic.

– May not work with rapid rotation.

– Arguments for mode saturation at lowpowers [Weinberg & Quatert 2008].

VULCAN/2D

Constraining the Core-Collapse SN Mechanism

C. D. Ott @ Caltech 01/2008 21

• Astronomical signature of core-collapse SNe very rich:

• Classical messengers: Can probe explosion morphology, energy, chemical composition, progenitor mass/size.-> May not be able to constrain details of the mechanism.

• Neutrinos and Gravitational Waves: Can probe high-density regime completely hidden from view by classical means.

– Neutrinos observed from SN 1987A confirmed general core-collapse picture. Today’s detectors would pick up many more events from a galactic/SMC/LMC core-collapse supernova.

– GWs not observed so far, but likely to be ideal messengers, carrying live information on the multi-D dynamics happening deep inside the SN core.

OpticalRadio, X/-raysNeutrinos

Nucleosynthesis yieldsPulsar kicksGravitational Waves

GW Emission Processes in Core-Collapse SNe


• Rotating core collapse and core bounce.

• Postbounce convection and SASI.

• Anisotropic neutrino emission.

• PNS core oscillations.

• PNS dynamical rotational 3D instabilities.

• Large-scale precollapse asymmetries.

Newtonian Quadrupole Formula:

The Signature of Core-Collapse Supernovae

in Gravitational Waves


Rotating Core Collapse and Bounce


• Collapse: Angular momentum conservation leads to spin up &rotational deformation of innercore.

• At core bounce: Very largeaccelerations -> rapidly changingmass quadrupole moment.

• Most extensively studiedGW emission in core collapse:

Ruffini & Wheeler 1971Thuan & Ostriker 1974,Saenz & Shapiro 1978-1981Moncrief 1979Mueller 1981Detweiler & Lindblom 1981Turner & Wagoner 1979

Seidel et al. late 1980sFinn & Evans 1990Moenchmeyer et al. 1991Bonazzola & Marck 1993Yamada & Sato 1995Zwerger & Mueller 1997Dimmelmeier et al. 2002Ott et al. 2004Shibata & Sekiguchi 2004

Newtonion & simple GR models


• 2 general type of dynamics, waveform morphology

• Type I: Pressure-dominated bounce.

• Type II: Rotation dominated, centrifugal bounce.

[Moenchmeyer et al. 1991, Zwerger & Mueller 1997, Dimmelmeier et al. 2002, Ott et al 2004 etc.]

New Results: Rotating Collapse and Bounce


[Dimmelmeier, Ott et al. 2008, Dimmelmeier, Ott et al. 2007, Ott et al. 2007ab]

• First 2D/3D GR simulations withhot microphysical EOS & deleptonization during collapse.

• GW signature determined by inner core mass, inner core angular momentum, and (to some extent) nuclear EOS.

• GW signal of generic shape;no “multiple centrifugal bounce”or fizzlers.

• GWs from “quickly” spinningcores (precollapse P0 < 10 s) “detectable” throughout the Milky Way.

• Important finding: Cores stay axisymmetric through bounce and early postbounce phase.

New Extended 2D GR Model Set


[Dimmelmeier, Ott, Marek, and Janka 2008 to be submitted to PRD, Dimmelmeier et al. 2007ab, Ott et al. 2007]

• >140 2D GR models with Ye(ρ) parametrization.

• 6 presupernova models.

• Slow to very rapid rotation.

• Solid-body to moderately differential rotation.

• 2 finite-temp. nuclear EOSs.

1) slow rotation, pressure-dominated

bounce, prompt convection

2) moderately-rapid rotation, pressure-

dominated bounce

3) rapid rotation, pressure-dominated,

rotation-influenced bounce

4) single centrifugal bounce.

Results• GW signature of rotating collapse

multi-degenerate.• Key parameters: Precollapse central Ω. Precollapse iron-core entropy.

• Classical picture: High T/|W| instabilities. Azimuthal modes exp(im). m=2 “bar-modes” (T/|W|)dynamical = 0.27, (T/|W|)secular 0.14.Numbers hold roughly in GR and moderate differential rotation.

PNS Spin and Rotational Instabilities

28

[e.g., Chandrasekhar 1969]

[Dimmelmeier, Ott et al. 2008 in preparation, Ott et al. 2007, Ott et al. 2006]

[e.g., Baiotti et al. 2007]


[Shibata et al. 2000, 3+1 GR simulations]

• Classical picture: High T/|W| instabilities. Azimuthal modes exp(im). m=2 “bar-modes” (T/|W|)dynamical = 0.27, (T/|W|)secular 0.14.Numbers hold roughly in GR and moderate differential rotation.

PNS Spin and Rotational Instabilities

29

[e.g., Chandrasekhar 1969]

[Dimmelmeier, Ott et al. 2008 in preparation, Ott et al. 2007, Ott et al. 2006]

[e.g., Baiotti et al. 2007]

• Can a realistic PNSs reach such high T/|W|?


• Direct numerical simulation:No – Collapsing cores hit rotational barrier.

• Critical T/|W| (secular/ dynamical) attainable during PNS cooling.

• Don’t forget MHD!

[Ott et al. PRL 2007 & CQG 2007, Dimmelmeier, Ott et al. 2008 in prep.]

• Dynamical rotational instability at low T/|W|.

• Dominant m=1 mode; m={2,3} modes mixed in (radial & temporal variation).

• Mechanism:Corotation instability (?)Resonance of unstable mode with background fluid at corotation point(s).

• Spiral density waves –relationship to accretion and galactic disks? -> angular momentum transport.

A Low-T/|W| Rotational Instability


[e.g., Centrella et al. 2001, Saijo 2003, Saijo & Yoshida 2006, Ott et al. 2005, Ou & Tohline 2006, Cerdá et al. 2007b]

• Note: PNS embedded in SN core and continuously accreting angular momentum. Cannot be described by an equilibrium NS model!

GW Emission, Model s20A2B4


Polar Observer +

Polar Observer xEquatorial Observer x

Equatorial Observer +

GW Emission vs. Detector Noise


• 3D component: lower in amplitude than core-bounce GW spike, but greater in energy! Emission in narrow frequency band around900—930 Hz (2 x pattern speed of the unstable mode!) models.

Switching Gears:

GWs emitted by Convection, SASI, Neutrinos,

Global Asymmetries,&

PNS core g-modes


(Most) Calculations performed with the axisymmetric Newtonian VULCAN/2D radiation-(magneto)hydrodynamics code.

*Livne et al. ‘93, ‘04, ‘07, Burrow et al. ‘06, ‘07abc, Dessart et al. ‘06,ab ’07, Ott et al. ‘06ab, ‘08+

Convection


[e.g., Janka & Müller 96, Burrows et al. 95, Mezzacappa et al. 98, Swesty & Myra 06, Dessart et al. 06 & references therein.]

• Prompt postbounce convection.

• Postbounce neutrino-driven convection in gain layer generic to all non- and slowly rotating SN cores.

• PNS core convection.

[Dessart et al. 2006][Ott et al. 2007]

GWs from Convection & SASI


m15b6; very slowly rotating

• Mixture of PNS and post-shock convection/turbulence.• Convection (partially) stabilized by rapid rotation (positive j gradient)• Broad-band, low-amplitude GW emission.• EGW < 10

-11 — 10-9 M c2

• In addition: low-frequency emission due to neutrinos. (not included here)

[Ott et al. 2008 in prep., Ott et al. 2006, Müller et al. 2004, Müller & Janka 1997]

GWs from Anisotropic Neutrino Emission


[Epstein 1978, Burrows & Hayes 1996, Janka & Müller 1997, Müller et al. 2004, Dessart et al. 2006, Ott 2006, Ott et al. 2008 in prep.]

• Any accelerated mass-energy quadrupolewill emit GWs. Anisotropic neutrino radiation:

• Anisotropic neutrino emission in core-collapse SNe:• Convective overturn: small-scale variations.• Rapid rotation: large-scale anisotropy.• Large-scale asymmetries: large-scale anisotropy.

[Ott

et

al.

20

08

Ap

Jsu

bm

itte

d!]

• GW“Memory”

[Dessart et al. 2006, Accretion-Induced Collapse

GWs from Large-Scale Precollapse Asymmetries


[Burrows & Hayes 1996, Fryer et al. 2004]

• Precollapse inhomogeneities in nuclear silicon/oxygen burning maybe large, leading to density perturbations O(10%). [Bazan & Arnett ‘97, Meakin et al. ‘06+.

• May result in asymmetric explosions (-> pulsar recoils) and emission of GW burst (with memory!) from mass motions and neutrinos.

• Somewhat unexplored: Only 2 studies; most stellar evolution is done in 1D. Would need large parameter study.

[Burrows & Hayes 1996]

Unstable Protoneutron Star core g-modes &The Acoustic Supernova Mechanism


• SASI-modulated supersonic accretion streams and SASI generated turbulence excite lowest-order (l=1) buoyancy mode in the PNS. Eigenfrequency f 300 Hz 30%.

[Burrows et al. 2006, 2007b/c, Ott, Burrows et al. 2006]

• g-modes reach large amplitudes 600—1000 ms after bounce.

• Damping by strong sound waves that steepen into shocks; deposit energy in the stalled shock.

• Drive 1 B explosions at late times.

GWs from PNS core g-modes:The GW Signature of the Acoustic Mechanism


s25.0 from Burrows et al. 2007

Core Bounce

Convection & SASI

early g-modes

late-time PNS g-modes

• Core bounce: Rotation,perturbations, prompt convection.

• Convection: PNS and -driven.

• g-modes: l=2 components emit GWs.

• But: g-modes maysaturate at low level. [Weinberg & Quatert 2008]

[Ott 2008, Ott et al. 2006]

GW Spectra and LIGO Sensitivity


[Ott 2008 in prep., Ott et al. 2006, Burrows et al. 2007]

• EGW 10-8 — 10-6 M c2 , one model 8 x 10-5 M c2.

• Progenitor mass (= accretion rate) dependence.

Time-Frequency Analysis of the GW Power Spectrum


Models s15.0WHW02

Putting Things together:

GWs as Indicators for the Core-Collapse Supernova

Explosion Mechanism


Mechanism GW Emission Process

Characteristic GW Signature

GWs as Indicators for the SN Mechanism


Mechanism /Feature

MHD Mechanism

Acoustic Mechanism

Neutrino Mechanism

Progenitor Rotation fast, P0 < 4 s none/slow none/slow

Core Bounce GWs

Convection/SASI GWs

Neutrino GWs

Rotational 3D Instability GWs

PNS g-mode GWs



Mechanism /Feature

MHD Mechanism

Acoustic Mechanism

Neutrino Mechanism


Core Bounce GWs strong

Convection/SASI GWs

none/weak

Neutrino GWs large h, low energy


strong, thoughcompetition with MRI

PNS g-mode GWs none



Mechanism /Feature

MHD Mechanism

Acoustic Mechanism

Neutrino Mechanism


Core Bounce GWs strong none/weak

Convection/SASI GWs

none/weak moderate


moderate h, low energy



none

PNS g-mode GWs none very strong



Mechanism /Feature

MHD Mechanism

Acoustic Mechanism

Neutrino Mechanism


Core Bounce GWs strong none/weak none/weak

Convection/SASI GWs

none/weak moderate moderate






none none

PNS g-mode GWs none very strong weak

• Galactic SN necessary with LIGO I, Advanced LIGO: Local Group

• Caution: Explosion mechanisms may “mix”!

The Sad Truth

Supernova Rates


Core-Collapse Supernova Rates


• Local group of galaxies: V 30 Mpc3

– Milky Way, Andromeda (M31), Triangulum (M33) + 30 small galaxies/satellite galaxies (incl. SMC & LMC).

• Local group: worst case 1 SN in 90 years, best case 1 SN in 20 years.

• Most local group events with 100 kpc from Earth.

• Next jump in rate around M82 at 3.5 Mpc.

Compiled fromlong list of references,e.g. Cappellaro et al., den Bergh & Tammann.

Nearby Core-Collapse Supernovae


Core-collapse SNe within 5 Mpcsince the beginning of LIGO operations:

M82 Chandra/HST/Spitzer composite.

M31 (Andromeda) Spitzer.

Ando et al. 2005

[Ott 2008in prep.]

SN 2008bk


• SN 2008bk (type II-p) discovered on 03/25/08. Core collapse between 02/15 and 03/05.

• LIGO L1 & H1 and VIRGO down. LIGO H2 and GEO600 in Astrowatch mode. B. Monard

• H2 & GEO600 should not have seen anything.Burst-search underway.

• Even LIGO 2 would have had trouble seeing a core-collapse SN at 4 Mpc.

Thanks:Erik Katsavounidis &Michael Landry

[Ott 2008in prep.]

Summary & Conclusions


• Multi-D core-collapse SN simulationsare beginning to mature; many produce explosions.First calculations in 3+1 GR.

• No agreement on the SN mechanism & many open questions (e.g., failing core-collapse SNe & long-soft GRBs etc.).

• Gravitational waves from a galactic/SMC/LMC SN mayhelp constrain the explosion mechanism. More distant SNe can help set upper limits.

• Rotating collapse/bounce waveforms becoming robust; other emission processes need more & better modeling.Waveform catalogs: http://stellarcollapse.org/gwcatalog

http://www.mpa-garching.mpg.de/rel_hydro/wave_catalogue.shtml

[see GW data analysis study by Summerscales et al. 2008 using Ott et al. 2004 waveforms]

Supplemental Slides


The C3W Code


[http://www.cactuscode.org]

• Cactus computational infrastructure.

• Carpet mesh refinement package.

• Ccatie (AEI-CCT) BSSN curvature evolution code. Γ-driver shift, 1+log lapse.

• Whisky finite-volume GR hydrodynamics code with PPM reconstruction.

• Finite-temperature nuclear Shen EOS.

Cactus/Carpet/Ccatie/Whisky

[http://www.carpetcode.org]

[e.g., Alcubierre et al. 2002]

[e.g., Baiotti et al. 2004, http://www.whiskycode.org]

[Shen et al. 1998]

[Liebendörfer 2005]• Simple deleptonization scheme for pre-bounce phase.

• Typically 9 levels of refinement; each 803 zones. 300 m central resolution; grid out to 3000 km radius. Corresponds to 8500 unigrid zones.

Core-Collapse Supernova Simulationswith the VULCAN/2D Code


• 2.5D (axisymmetric) Newtonian (magneto-)hydrodynamics.

• Unsplit arbitrary Eulerian/Lagrangian scheme.

• Newtonian Self gravity.

• Neutrino Radiation Transport:

– 2 versions:Flux-limited diffusion &Boltzmann transport.

– Multiple energy groups,νe, νe, “νμ” species.

VULCAN/2D Grid

[Livne 1993, Livne et al. 2004, Livne et al. 2007, Burrows et al. 2007]

GW Emission from AIC


• Neutrino component dominates in amplitude, but not in energy.

• Rotation yields largest possible anisotropy!

57

MHD jet/explosion launched when Pmag / Pgas 1

Features/Limitations of the MHD Models

C. D. Ott @ ECT* Trento Workshop «Matter at Extreme Densities and GWs from Compact Objects », 09/2007 58

• Jet powers up to 10 B/s (1052 erg/s).

• Simultaneous explosion and accretion.

• Hypernova-energies (> 10 B) attainable.

• MHD mechanism inefficient for cores with precollapse P0 > 4 s, but stellar evolution + NS birth spin estimates: P0 > 30 s in most cores.

• MHD explosion — a GRB precursor?

• Limitations: Resolution does not allow resolution of MRI effects; 2D; Newtonian.

[Heger et al. 2005, Ott et al. 2006]

[Burrows et al. 2007]

Features of the Acoustic Mechanism


• A Tale of Two Instabilities: SASI and core g-mode.

• Inner core acts as transducer of accretion power into acoustic power.

• Late explosions (0.5—1.2 s after bounce).

• Explosions fundamentally aspherical: unipolar?

• Simultaneous explosion and accretion.

• Role of neutrinos important: setting the stage & contributing to total explosion energy.

• Site for r-process nucleosynthesis?

• Pulsar kicks?

blowing up massive starsaspen08.gravity.psu.edu/program/ott_aspen_mai_2008.pdfc. d. ott @ aspen, may...

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