From the whistle of a kettle
to the asymmetric explosion of supernovae
Fep+, n, e-p  e  n   eshock~150km

en   e  p  e neutrinosphereT. Foglizzo, CEA Saclay
T. Yamasaki, J. Sato, J. Guilet
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The family of advective-acoustic instabilities
supersonic black holecellular detonation

whistling kettle

Ariane 5Ruffert 1994

Timmes et al. 2000

Scheck et al. 2004

asymmetric supernova

2Outline

Core-collapse supernovae, before and after SASI (2003)

How far do we understand SASI ?
->the link with whistling kettles

Observational constraints
Perspectives

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The difficult energy budgets of supernovae(orders of magnitude)

Collapse of the core of a massive star to a neutron star (SNII, Ib/c): Egrav>>EK
but ...
essentially carried away by neutrinos

White Dwarf thermonuclear disruption (SNIa) : tight budget

4Core-collapse supernovae: delayed explosion mechanism(Bethe & Wilson 1985)(A. Burrows)

but ... inefficient in 1D (Liebendörfer et al. 2001)

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Core-collapse supernovae in 2003: « What was missing? »QuickTime™ and a
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Buras et al. 03

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Stationary Accretion Shock Instability : SASI
Blondin et al. 03

ep  e  n  eshock~150km


neutrinosphere

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the mechanism of SASI must be fundamentally different from neutrino-driven convection(Foglizzo et al. 06, Yamasaki & Yamada 07)-> an advective-acoustic cycle ? (Blondin et al. 03, Galletti 05, Ohnishi et al. 2006, Foglizzo et al. 07, ...)

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- advected perturbations- acoustic feedback

Aero-acoustic instabilities• vortical-acoustic cycle

sonvorticité

whistling kettle
Chanaud & Powell (1965)

vibrations in Ariane 5
Mettenleiter, Haile & Candel (2000)• entropic-acoustic cycle

soundentropy
nozzlecombustion

rumble instability of ramjets
Abouseif, Keklak & Toong (1984)

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SASI in numerical simulations: ubiquitous since 2003
initialsettingsymmetrySASI-driven
convection

NSg-modes

2003

Blondin et al.

stalled

2D axi.

X--

2004

Scheck et al.

collapse

2D axi.

X

X-

2006

Scheck et al.

collapse

2D axi.

X

X-

Burrows et al.

collapse

2D axi.

X

X

X

Ohnishi et al.

stalled

2D axi.

X

X-

Blondin & Mezzacappa

stalled

2D axi.

X--

Blondin & Mezzacappa

stalled3D

spiral--Kotake et al.

stalled

2D axi.

X

X-

Burrows et al.

collapse

2D axi.

X

X

X

Blondin & Shawstalled2D eq.

spiral--Fryer & Young

collapse

3DX

X

?

Scheck et al.

collapse

2D axi.

X

X-

Iwakami et al.

stalled3DX

X--

Marek & Jankacollapse

2D axi.

XX

weak-

Ott et al.

collapse

2D axi.

XX?

-Murphy & Burrows

collapse

2D axi.

XX?

2007

2008

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Unexpected consequences of SASI
-successful explosion mechanism based on neutrino energy
deposition, 15Msol (Marek & Janka 08)

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- new explosion mechanism based on acoustic energy, 11-25Msol(Burrows et al. 06, 07, Yoshida et al. 2007, Weinberg & Quataert 08)- pulsar kicks (Scheck et al. 04, 06, Iwakami et al. 09)- pulsar spin
(Blondin & Mezzacappa 07, Yamasaki & Foglizzo 08, Iwakami et al. 09)- H/He mixing in SN1987A (Kifonidis et al. 06)- additional source of gravitational waves

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(Ott et al. 06, Kotake et al. 07, Marek et al. 08, Ott 08)

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Observational constraints on the explosion mechanismHobbs et al. 05

Scheck et al. 06

Velocity distribution of pulsars

Kick-spin alignement (Wang, Lai & Han 06, Ng & Romani 04)
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Explosion asymmetry deduced from-spectropolarimetry (Leonard et al. 06, Wang et al. 03, ...)
-oxygen spectroscopy (Maeda et al. 08)

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SNR composition gradients ? (Katsuda et al. 08)
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SASI in 3D: dominated by a spiral mode ?
even if the progenitor is not rotating ?

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Blondin & Mezzacappa 07, Iwakami et al. 08, 09

If the spiral mode of SASI always dominates thesloshing mode, what is the relevance of all previous
2D axisymmetric simulations ?
-> successful 2D explosion mechanism(s) ?

-> successful 2D pulsar kicks ?
-> prediction of kick-spin misalignement ?

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Should we trust the simulations of SASI ?
Existing debates about- the explosion threshold- the growth of the neutron star g-mode- the kick amplitude- the spiral mode of SASI in a non-rotating progenitor-> Validation of the simulations of SASI in the linear regime

growth rate

Blondin & Mezzacappa 06, Foglizzo et al. 07

shock distanceDo we really understand the mechanism of SASI ?

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Advective-acoustic cycle in a decelerated, cooled flow

growth rate

Foglizzo et al. 07

Hoscillation frequency

He

Unstable advective-acoustic cycle,
Stable acoustic cycle

QR

oscillation frequency

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Advective-acoustic cycle in a simplified core-collapse (Scheck et al. 08)

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Rc~R∇

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The simplest example of a 2D advective-acoustic cycle

16Acoustic feedback generated by the decelerationof a vorticity wave (Sato, Foglizzo & Fromang 08)

H

He

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Explicit analytical expressions for the coupling efficiencies (Foglizzo 08)

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Numerical check of analytical formulae (Sato, Foglizzo & Fromang 08)

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Numerical convergence: only linear at the shock (Sato, Foglizzo & Fromang 08)20

Understanding the efficiency of the acoustic feedback (Foglizzo 08)

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-high frequency: stabilized above the cut off-high l: evanescent pressure feedback->SASI is a low frequency, low l instability21

Effect of core rotation on SASI in a cylindrical flow

(Yamasaki & Foglizzo 08)- Growth rate of the spiral modeH

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First order effect of rotation:- negligible centrifugal force -Doppler shifted frequency -m
Domination of the spiral mode without rotation ???

He- WKB interpretation
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Conclusions

SASI in 2D is able to produce - a successful neutrino driven delayed explosion- a powerful pulsar kick
The mechanism responsible for SASI is the advective-acoustic cycle(the same family as the whistling kettle)
A toy model can explain why SASI is a low frequency, low l instabilityA « moderate » progenitor rotation favours the spiral mode of SASI in 3D
Numerical difficulties associated to the- lower boundary condition- shock treatment/grid size

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Some open questions

Numerical confirmation of 2D results: explosion, kick ?
How marginal is the spiral mode of SASI ?

3D-spiral mode even without core rotation ?
-successful neutrino driven explosion in 3D ?
-powerful kick in 3D ?

-kick-spin misalignment ?

Towards a MHD SASI ?
Energy and momentum budget of SASI ?

More observational constraints ?

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