Explosion Mechanisms of

Core-Collapse Supernovae:

perspectives for

multi-messenger astronomy

超新星と超新星残骸の融合研究会

-恒星進化・爆発メカニズムと元素合成

Kei Kotake （National Astronomical Observatory of Japan)

with Tomoya Takiwaki (NAOJ),Yudai Suwa (Kyoto),

Takami Kuroda (NAOJ), Ko Nakamura (NAOJ), Akihiro Suzuki (NAOJ),

, and Youhei Masada (Kobe)

Outline

✓ Part 1 : Tutorial (30 min)

§1-0 Overview & general introduction

§1-1 Physics of Core-Collapse Supernovae

:what is the essence to blow up massive stars?

§1-2 Candidate mechanisms: based on the state-of-the-art

numerical simulations

✓ Part 2 :Observational Signatures (20 min)

✓ Signatures and detectability of

gravitational waves and neutrino emission

✓ Perspectives for “MM” astronomy (correlation analysis between GWs/neutrinos, electromagnetic messengers)

What can we learn from the central engine ?

De Laney et al. (2010)

Cas A Fe

Long-lasting questions (1/3)

Final goal (1): Origin of the explosion asymmetry ?!

: Origin of heavy elements

(e.g., see talks by Wanajo-san, Tominaga-san, Ono-san !)

✓Seed Asymmety: SN dynamics, mixing instability (unclear yet)

✓Final goal (2): Toward “MM” astronomy:

“Consistent modeling” from the center to SNRs is numerically

challenging !

Long-lastgin questions(2/3) ? First-principle 3D simulation:

Takiwaki, KK, Suwa (2012)

Approximate 3D simulation:

Scheck et al. (2009)

9000 km

Piston model:

Hammer et al. (2011)

7.5 e7 km

500 km

Long-lasting questions(3/3) ?

✓Final goal (3) : To reproduce the canonical explosion

energy of 1 Bethe (= 1051 erg)

(Ultimately) : To understand the bifurcating trend !

Nomoto et al. (2003), Tanaka et al. (2009)

§1-1

The standard supernova theory

:Dynamics from gravitational

collapse to explosion

core collapse

H

HeC+O

Si

Fe

trapping core bounce

NSNS

shock propagation in coreshock in envelopeSN explosion

Standard scenario of core-collapse SNe

✓ Gravitational collapse starts in the iron core.

(e.g., Kotake+06, Janka+07 for a review)

K.Sato (1975)

core collapse

H

HeC+O

Si

Fe

trapping core bounce

NSNS

shock propagation in coreshock in envelopeSN explosion

Standard scenario of core-collapse SNe (e.g., Kotake+06, Janka+07 for a review)

Neutrino sphere

Neutrinos are trapped inside the “neutrino sphere”

K.Sato (1975)

core collapse

H

HeC+O

Si

Fe

trapping core bounce

NSNS

shock propagation in coreshock in envelopeSN explosion

Standard scenario of core-collapse SNe

✓ Gravitational collapse starts in the iron core.

(e.g., Kotake+06, Janka+07 for a review)

Neutrino sphere

Neutrinos are trapped inside the “neutrino sphere”

Stiff !

Radial velocity profile based on 1D radiation-transport

simulations

K.Sato (1975)

core collapse

H

He C+O

Si

Fe

trapping core bounce

NS NS

shock propagation in core shock in envelope SN explosion

Standing

Accretion shock

✓Have to find the way to revive the stalled bounce shock.

✓ The best-studied & most promising:

the neutrino-heating mechanism (Bethe, Wilson 1985)

: neutrinos heat material to produce explosions.

✓ Except for special cases(Kitaura + (06)), the simplest,

1D form of this mechanism does not work. (Liebendoerfer et al. (2001), Rampp & Janka (2000), Sumiyoshi et al. (2005))

Standard scenario of core-collapse SNe

Neutrino sphere

Iron core

２０yr

Proto-Neutron Star (PNS)

shock

(Wilson 1985)

(Rampp & Janka 2002)

（Liebendoerfer et al. 2003)

(Sumiyoshi et al. 2004)

Looking back 20+ Years of Modeling & Theory

Multidimensional modeling is crucial !

Iron core

２０yr

Proto-Neutron Star (PNS)

shock

(Wilson 1985)

(Rampp & Janka 2002)

（Liebendoerfer et al. 2003)

(Sumiyoshi et al. 2004)

Looking back 20+ Years of Modeling & Theory

M

HST image

Maeda et al. (2008)

CCSNe are aspherical.

Multidimensional modeling is crucial !

Stalled shock

10 km Stellar radius

Heating rate

cooling rate

~200km

Cooling rate ~ R^{-6}

Heating rate ~ R^{-2}

PNS

Cooing domintated

Heating domintated

~ 100 km (Gain Radius)

Why no explosion in 1D (1)？ heating

cooling

with T~1/R

Neutrino sphere

Stalled shock

~200km

Cooling-dominated

Heating-dominated

(Gain region)

PNS

In spherical symmetry

＜

＞

Advection timescale Neutrino heating timescale

No explosion!!

In multi-dimensional simulations （convection, SASI）

could be satisfied !

Why no explosion in 1D (2)？

heating

cooling

Thompson et al.(05)

Ohnishi et al. (06)

Marek & Janka (09)

(Standing Accretion Shock Instability)

PNS

M Standing shock

Lν

５０ｋｍ

Tantalizing problems in 1D

Burrows & Goshy(93)

PNS

M Standing shock

Lν

５０ｋｍ

Tantalizing problems in 1D

Burrows & Goshy(93)

Energy budget problem in the neutrino heating mechanism

Releasable energy = binding energy of neutron star, essentially carried away by neutrinos.

For the neutrino heating mechanism working,

・ ~1% energy transfer via neutrinos to matter.

.

Typical observed explosion energy：

✓ Have to deal with 6D Boltzmann transport

（fermion・σ~ε2, coupling between energy/angle)

✓ over the entire simulations (for 2D, ~10^{20} operations,

1 CPU year/ one simulation @ 10Tflops supercomputer.) → A grand challenge in computational astrophysics !

(e.g., Kotake (2011), Kotake et al. (2012a,b) )

A list of recent “rad-hydro” milestones making “explosions”

Current paradigm: multi-D neutrino-heating mechanism

✓After bounce, the bounce shock stalls.

✓ “Standing Accretion Shock

Instability (SASI)” develops.

✓ The dwell timescales of matter in the

gain region ⇒ much longer in multi-D.

✓ At around O(100)s ms after bounce,

the neutrino-driven explosion occurs.

Suwa, KK+ (10,11) 15 Msun star (WW95)

✓2D rad. hydro core-

collapse simulation with spectral

neutrino transport

✓Lattimer-Swesty EOS

(K=180MeV)

Color map: entropy

1000 km (~size of Fe core)

(see Janka (2012), Kotake et al. (2012) for recent reviews)

Y.Suwa (KITP）

Ye profile in our 2D models (pioneered by Arcones et al. (2006)

Fischer et al. (2010,2011), Arcones & Janka (2011))

In the beginning of the neutrino-driven wind phase

(tpb ~ 550 ms for 15 Msun progenitor (WW95))

✓The neutrino-driven wind ⇒ proton-rich in multi-D simulations.

(Interested in our multi-D data , Emails, start collaboration !)

✓ Link of MHD models to r-process cites (yet explored in great detail !)

Takiwaki & KK (2011)

Magnetic

field line

Suwa et al. (2012)

List of recent milestones reported “explosions”

✓ Different SN groups have a tendency to employ

different progenitors with different transport schemes and

different EOSs, …and providing different results…..

✓ Detailed comparison is needed !

✓ Systematic study (see Suwa’s talk tomorrow !)

(e.g., Kotake (2011), Kotake et al. (2012a,b) )

✓ Still (a little) behind to successfully produce explosions

as energetic as 1051 erg.

✓ “Something” may be missing ….

✓ 3D hydro and general relativity : the final frontier !

3D Core-Collapse Supernova Simulations

(Long history: Shimizu, Yamada, Sato (1993), Kotake, Iwakami + (2009))

解くべきはBoltzmann equation左辺：ニュートリノ数の変動

右辺：衝突項(Collisional term)

反応によるニュートリノ数

の変動

f (t,r,,,E,p,p )

ER (t,r,,,E) dp dp f

ER (t,r,,) dE dp dp f

“MGMA”(6 dimensional problem)

“MG”(Multi energy-Group：エネルギー群） ) or IDS(isotropic diffusion source approximation)

“Gray (no energy-dependence)”

資源不足

近似×

◎

輻射輸送基礎方程式： IDSA法(Liebendoerfer et al.(2009))

（２成分流速制限法）

輻射は implicit・流体は explicit

空間3次元＋ニュートリノ位相空間1次元のシミュレーション

Tomoya Takiwaki

Visualization：Tomohide Wada

(4D2U)

Our most up-to-date 3D results

Takiwaki, KK, and Suwa (2012) ApJ

✓ 11.2 Msun progenitor (Woosley, Heger, Weaver (2002))

✓ Spectral neutrino transport is solved (IDSA: Liebendoerfer+09)

✓ 320(r)x64(θ)x128(φ)x20(ε) (4 times finer than our ApJ paper)

✓ 8192pararell x 3 CPU weeks @ “K” computers.

Click here for animation

Comparison of average shock radii

Dim. r x Θ x Φ x ε

3D: 320x64 x128 x 20

3D low: 200x32x 64 x 20

2D : 320x64 x 20

1D: : 320 x 20

✓ Our 3D model with highest resolution

⇒ most energetic shock propagation!

11.2 Msun star

Easy to obtain explosions in 3D ?(Yes and No!)

✓For working the

neutrino-heating mechanism

The residency timescales become longer

in 3D than in 2D.

✓From the hydrodynamic point of view,

it would be more easier for 2D. ２Ｄ

３Ｄ

Marek & Janka (2012) Suwa et al. (09) Kotake et al. (09) Iwakami et al. (08)

Stay tuned for our

high resolution 3D simulations using

the K computer !!

(640x128x256x20)

Moderately rotating model

11.2 Msun star (P0 = 4 s)

Bipolar explosions:

✓Explosion energy

higher !

✓ Nucleosynthesis,

neutrino, and

GW signatures

between rotating

and non-rotating

models exciting !

Non-Rotating

1D 3D

Gray

Multi-

Energy

Adia

-batic General relativity

2D

GR 3D

GR

Mueller et al. (2012)

Kuroda + (2012)

Short summary toward ultimate 6D SN simulations

Iwakami+08,09 Ohnishi+07

Burrows+07 Bruenn+09

Marek & Janka 09

Ott+08

Murphy

& Burrows

+08

Fryer et al. 02

Fernandes 09

Blondin + 03 Blondin + 07

Nordhaus et al. 2010

Hanke et al. (2011) Wongwathanarat + (08)

Takiwaki et al. (2011)

Suwa+09,11

Obergaulinger &Janka(10) 15 Msun progenitor (WW95)

✓ K. Thorne’s momentum

formalism for GR M1

transport (Thorne 1981,

Shibata + 2011).

Color : entropy

Linear scale

Is general relativity (GR) helpful for explosions !?

Kuroda, KK, Takiwaki (2012), ApJ

Comparison of average shock radii

✓Except for our 3D-GR model, the shock has shown a trend of recession.

✓ why ? Neutrino energy and luminosity increases due to stronger gravity !

(SR:special relativity)

(GR:special relativity)

15 Msun (WW95)

(see also B.Mueller+12)

Diagnostic of explosion : residency timescale/heating timescale

✓The combination of 3D and GR

⇒ the most supportive condition of explosions !

✓ In order to extract hydro-data for nucleosynthesis…

✓1000ms/(2 ms per day) ~ 500 days…

Summary of current status of SN mechanism

Energy-drivers for explosions:

☆Neutrino heating mechanism

aided by convection/SASI

(Marek & Janka 09, Suwa et al. 10, Takiwaki+12)

also aided by rotation

(KK+03,06, Walder+05,Ott+08, Suwa et al. 10)

☆Acoustic-power

Acoustic mechanism:

（Burrows+. 2005,6, Ott+07)

☆ Extraction of rotational energy via B-fields

MHD models: (LeBlanc & Wilson (70), Symbalisty (84),

KK+04, Takiwaki+05 Shibata+06, Obergaulinger+06,

Cerda Duran+07, Burrows+07, Suwa+07,

Takiwaki+08….)

Explosion

Likely !

(but the

explosion energy

is still less than

10^{51} erg..)

3D and GR needed!

Strong explosion!

but remains

uncertain.

Jet-like explosion! (relevance to

magnetar or Collapsar), but minor

(< 1% of all supernovae) .

☆ Which one is the final answer ?

☆ To pin down the proposed explosion scenarios,

⇒important to discuss a connection to observables!

✓supernova nucleosynthesis

✓gravitational-wave (∝1/R) and neutrino astronomy (∝1/R2)

Primary observables: “direct” information of engine

§2: Multi-messengers from

Core-Collapse Supernovae “Multi-Dimensionality as a key to bridge theory and observation”

One Slide for Gravitational Waves (GWs)

y

z

represents the degree of anisotropy.

What makes the SN-dynamics deviate

from spherical symmetry ?

☆ A back-of-envelope estimation

GW amplitude

(see reviews in Kotake et al. (2006), Ott (2009), Fryer & New (2011), Kotake (2011))

✓CCSN in our galaxy are the target of GWs

z Multidimensionality

(origin of anisotropy)

GW emission Explosion dynamics

✓Dream is…

“To clarify the long-veiled

explosion dynamics of CCSNe

(and collapsars)

via GW observations ! “

✓ Theoretically we have to

understand the expl. dynamics !

(e.g., Kotake et al. (04), Obergaulinger et al.(06), Shibata et al.(06), Takiwaki & Kotake (11))

Gravitational-wave features in MHD explosions

Bounce signals

✓ In the MHD exploding models, the

gravitational waveforms

show an increasing trend after bounce.

✓The MHD mechanism works only if

pre-collapse core has

rapid rotation (P0 < 4 s) and

strong magnetic fields(B0>10^{11}G).

✓ GW amplitudes from prolately

expanding material positively increase

Takiwaki & KK (2011) Rotational

axis

Magnetic

field line

Gravitational waveform from MHD explosion

Gravitational waveforms in 3D simulation with spectral transport

(see also, Mu”ller & Janka (1997), Ott(2009), KK et al. (09,11), Mueller et al. (2012))

Total amplitudes (matter + neutrino) Neutrino only

Prompt convection

2D model Total amplitudes

(matter + neutrino)

Neutrino only

✓The total amplitudes in 3D become ~ one-order-of magnitude

smaller than those in 2D, however within the target for

the next-generation detectors (like KAGRA and adv LIGO).

@10kpc

KK + in prep

Comparison of Waveforms between candidate mechanisms

(KK et al. 09, KK et al. 11)

Burrows

+06

Acoustic-wave mechanism

Ott+06

Burrows

+06

Acoustic-wave mechanism

Ott+06

Bounce signalsBounce signals

MHD feature

MHD mechanisms (Takiwaki and KK 10)

A clear correlation:

between the explosion mechanism and the GW signals !

@10kpc@10kpc

Current detector

Upcoming

detector

GWs from

neutrino-driven SN (KK+09)

Detectability of GW signals

MHD

Take-take messages

(1) To detect these signals for a Galactic source,

the next generation detectors (KAGRA, adv. LIGO, 2015~) needed.

A

Acoustic

Mechanism

(Burrows+07

Ott+06)

Les Miserable: Nearby CC SNe

CCSNe within 5 Mpc since the

operation of the LIGO

MHD

Acoustic Take-home message (2):

✓ Horizon to advanced-class

detectors extends to ~Mpc

Logue+(2011)

Logue+(2011)

Take-home message (3):

✓ Spectrum analysis will tell

us the dynamics of the

engine (power-excess method)

Murphy+(08)

@10kpc@10kpc

Current detector

Upcoming

detector

GWs from

neutrino-driven SN (KK+09)

Importance of multi-messenger approach

MHD

☆By only by GWs, it is difficult to tell the difference between them.

☆Coincident analysis of GWs, neutrinos, and electromagnetic messengers

should be important for breaking degeneracy!

(see e.g., KK + (2012) for a review)

A

Acoustic

Mechanism

(Burrows+07

Ott+06)

If a supernova occurs tomorrow?

SN 20XX !

“in the Galactic center”

Large Detectors for Supernova Neutrinos

Super-Kamiokande (104)

KamLAND (330) MiniBooNE (200)

For a galactic SN

LVD (400)

Borexino (80)

IceCube (106)

arXiv:1108.0171

Neutrino and GW signatures between 3D models with/without rotation Takiwaki et al. in prep (see also Lund+10,12)

Electron-type neutrino Anti-electron-type neutrino

Spectrum

(P0 = 4 s) (P0 = 4 s)

✓Variation timescale of neutrino signals reflect the activity of SASI and

:neutrino-driven convection: longer for rotating models

⇒would provide one additional clue : the difference between

the rotating and non-rotating model.

Neutrino signatures in MHD explosion of supernovae Kawagoe et al.JCAP(2009), Kotake et al. (2012)

High resonance

Low resonance

Ev

ent

rate

[ /

sec]

Event rate ofe

Time [sec]

polar direction

equatorial

direction E

ven

t ra

te [

/se

c]

@SK

Inverted mass

hierarcy

Time [sec] polar direction

equatorial

direction

@ SK Event rate ofe

✓ These features are inherent to MHD explosions.

✓ Good measure to tell the difference from other scenarios.

Earth （Earth effect）

Supernova neutrinos

Neutrino emissionNeutrino emission

MSW effectMSW effect

SelfSelf--interactioninteraction

✓ Exposed to environments outside the central engine

✓ Neutrino oscillations are also dependent on the neutrino parameters.

(mixing angles, mass squared differences and mass hierarchy).

⇒ Rather indirect for the SN mechanism

✓ Could have a great impact on the elementary physics

✓ Useful as a tomography, i.e., the time evolution of the SN dynamics!

(see reviews for KK+06, Dighe+09)

Takahashi+06Takahashi+06

ν e

ν xν e

ν e

ν xν eν e

Supernova Neutrinos

Exp. Mechanism Neutrino Parameters

Gravitational Waves

Nucleosynthesis

Numerical Modeling

“Three eyes” to decipher the SN mechanism!

milliseconds 0 seconds（？） ＞hours

Convection SASI G-mode?

GWs

bounce

Time

Neutrinos

Expected event number Shock-revivals (?)

Nucleosynthesis

Electromag. rad.

X-ray,

optical,

radio..

MAXI

The gap is now being bridged !

Origin of Pulsar Kicks

モデルの数

Kick velocity Could explain the bimordal features.

外挿

（いくつかのモデルは

長時間進化を追っておいて）

Scheck et al. (2004,06)

v=90 km/s (40%)

500 km/s (60%)

✓ Heavy element

synthesis may

occur strongly

opposite direction

of the kick.

Electromagnetic messengers from CC supernovae

Ni56-rich

Si28-rich

O16-rich

1.5s

✓Explosive nucleosynthesis in SASI-aided 2D explosions

Si-rich jets, as in Cas A ? Si in Cas A

(NASA)

Matter Mixing

O16-rich

O16-rich

Ni

Si O

Spherical model

(Fujimoto, Kotake + 2011)

✓Explosive nucleosynthesis

occurs more drastically

along the direction of explosion

✓ This may account for

some observational features

such as in Cas A and SNR.

(Kifonidis et al. (2003,2006), Hungerford et al. (05), Young et al. (2006), Maeda et al. (2008))

Summary of “SN Multi-messengers” (Kotake +12)

Perspectives on “SN Multi-messengers” (Kotake +12)

BH-forming SNe

Bounce signals

Black hole formation

Ott et al. (2011) PRL

Fischer et al. (2008) A&A

LS EOSSHEN EOS

✓A correlation analysis of these messengers should be

very important to get a unified picture of stellar

collapse that bifurcates between NS or BH forming SNe!

✓ Multi-dimensionalities(convection, SASI, rotation, B-fields)

hold a key to bridge the SN theory (incl. nuclear theory) and

these multi-messenger observation.

Light-curve asymmetry at the shock-breakout signatures Preliminary

with A.Suzuki, M.Takana (pioneered by Kifonidis+2003, Hammer+10)

✓Detectability ?

✓Relevance to late-time

asymmetry ?

✓Integrated analysis ?

L = 2.5x 1052 erg/s

(rapidly rotating:

Ω0 = 0.5 pi rad/s)

K. Nakamura et al.

☆ On the 3D effects:

✓ Systematic studies in the first-principle 3D

simulations by changing resolutions, perturbations,

and so on) should be done !

⇒ Need peta- or exa-scale supercomputers! (see our recent review (accepted to PTEP: Kotake et al.

toward 6D simulations with exact Boltzmann transport in full general relativity !)

☆ Our 1st generation GR results: the combination of

GR and 3D provides the most favorable condition.

☆ Significantly further to reach the goal !

☆ Theoretical prediction of nucleosythesis, GWs, neutrinos

will be all updated by forthcoming simulations,

stellar evolution calculation !

☆ Hoping this conference to provide us with an opportunity

to bridge the gap between us !

Summary and Outlook

Thank you very much !

☆ On the 3D effects:

✓ Systematic studies in the first-principle 3D

simulations by changing resolutions, perturbations,

and so on) should be done !

⇒ Need peta- or exa-scale supercomputers! (see our recent review (accepted to PTEP: Kotake et al.

toward 6D simulations with exact Boltzmann transport in full general relativity !)

☆ Our 1st generation GR results: the combination of

GR and 3D provides the most favorable condition.

☆ Significantly further to reach the goal !

☆ Theoretical prediction of nucleosythesis, GWs, neutrinos

will be all updated by forthcoming simulations,

stellar evolution calculation !

☆ Hoping this conference to provide us with an opportunity

to bridge the gap between us !

Summary and Outlook