4th DTA Symposium on
Compact stars and gravitational wave astronomy
2016/05/13 at NAOJ

Gravitational Signals from Core-collapse Supernovae:

Cutting-edge samples

Tomoya Takiwaki(National Astronomical Observatory of Japan)

1Collaborators:
Takami Kuroda,
Kazuhiro Hayama andKei Kotake

GW from Supernova
Purpose: Signal gives information of deep inside of the star

GWs is the key to understand the mystery of SNe2

Difficulty:
Supernova:
deathof the star
 Rare event: 1-3 /(100 year)the/( 1galaxy)=>I believe our luck.
 Complicated waveform.
=> Spectrogram can compensate.
Advantage: ν is simultaneously detected. That helps theinterpretation
the signals.
Long lasting ofmystery:
How theexplosion
 Opticalcounterpart isoccur?
obviousGWGW from Supernovae
Purpose: Signal gives information of deep inside of the star

GWs is the key to understand the mystery of SNe

3

Difficulty: Rare event: 1-3 /(100 year) /( 1 galaxy)=>I believe our luck. e.g. 1987a Complicated waveform.
=> Spectrogram overcomes this weak point.
Advantage: ν is simultaneously detected. That helps theinterpretation of the signals.
 Optical counter part is obvious

Several typical situations
Explosion mechanism depends on the profile of the progenitor

Hayama+2015

Non rotatingrotating

We consider three typical situations.
(1) No rotating no magnetic progenitors(2) Rotating no magnetic progenitors(3) Rotating magnetic progenitors4Ω and B

Like BHs?
Schwarzschild
Kerr
Kerr-Newman

Two typical cases
 Non rotating progenitor

Explosion Mechanism
2. 2D simulations
3. 3D simulations1.

 Rapidly rotating progenitor

Axisymmetric simulations
2. Non Axisymmetric simulations
1.

5

Entropy

6

Key aspects of Neutrino Mechanism
Radial Velocity
Postshockedn,pPressureShock
PreshockedFeRam Pressure

RadiusEntropy~T^3/ρ
ProtoNeutronStar
7

Fe=>n, p

Heated by cooled by photoneutrino dissociation

When the shock is stalling,
Pressure inside and rampressure out side balances.

RHS is determined by stellar
structure(density profile).
LHS is determined by twoingredients.
(1) Photo-dissociation(2) Neutrino HeatingProblemSupernova shock in simulation
tends to stall anddoes NOT explode.

capiceCold waterLong-lasting Problem ~1980.
In 2000-2005, state-of-the-art
simulations with detailed
neutrino transport confirm that!
(Liebendoerfer+2001, Rampp+2002,Thompson+2003 and Sumiyoshi+2005)

8Hot water
Microwave oven(in 1D)Neutrino heating < ram pressure=> fails to explode!

9Key aspects of Neutrino Mechanism
Entropy~T^3/ρconvectiveEnergy transport

Fe=>n, pProto
NeutronStar

Heated byneutrinocooled byphotodissociation

Negative entropy gradientleads Rayleigh-Taylor
instability(Cold heavy matter is put overHot light matter)

Rayleigh-Taylor convectiontransfer energy outward.

Radius10

Cooler than
the initialstate but νheat is active

Hotter than
the initialstatecapice
Cold waterConvection!

Hot water
Microwave oven

11

Shock radius[km]Successful 3D simulation
11.2M_s

3D
1D

Time[ms]
2 month times 16,000 cores areused in K computer

With convection hot water at the bottom is transported
near the cap. The pressure at the cap become higher.
Explosion occurs with the process. Takiwaki+2012,2014, in prep

Two typical cases
 Non rotating progenitor

Explosion Mechanism
2. GWs from 2D simulations
3. GWs from 3D simulations1.

 Rapidly rotating progenitor

GWs from Axisymmetric simulations
2. GWs from Non Axisymmetric simulations
1.

12

Typical Models in 2D sim.

Radius [km]Entropy

Time after bounce [s]Time after bounce [s]Early Quasi periodic signals
2. Quiescent phase
3. Stochastic GW signal (before and after the shock revival)
4. low-frequency tail signal
1.

13

Mueller+2013

Typical Models in 2D sim.

Time after bounce [s]Early Quasi periodic signals
2. Quiescent25-50 km,phaseanisotropic motion and3. Stochastic
GW signal (before and after the shock revival)
acoustic waves
4. low-frequency tail signal
1.

14Mueller+2013

Typical Models in 2D sim.

Time after bounce [s]Time after bounce [s]Early Quasi periodic signals
2. Quiescent phase
3. Stochastic GW signal (before and after the shock revival)
4. low-frequency tail signal
1.

15

Mueller+2013

Typical Models in 2D sim.
ShockConvection& SASI
Unstable

Accrete to PNS
StableTime after bounce [s]Early Quasi PNS
periodic signals
GW
2. Quiescent phase
3. Stochastic GW signal (before and after the shock revival)
4. low-frequency tail signal
1.

16

Mueller+2013

Typical Models in 2D sim.

Time after bounce [s]Time after bounce [s]Early Quasi periodic signals
2. Quiescent phase
3. Stochastic GW signal (before and after the shock revival)
4. low-frequency tail signal
1.

17

Mueller+2013

Two typical cases
 Non rotating progenitor

Explosion Mechanism
2. GWs from 2D simulations
3. GWs from 3D simulations1.

 Rapidly rotating progenitor

GWs from Axisymmetric simulations
2. GWs from Non Axisymmetric simulations
1.

18

3D simulation
Kuroda et al. in prep
15M_sGR
Leakage19↓Fourier Transformations. Spectrogram.

20

Neutrino EAmplitude

GW from 3D simulations

Origin of GW(1):g-mode oscillation at PNS surface
Shock
Convection& SASI
Unstable

Accrete to PNS
Stable

M: Mass of PNS
Mueller+13
R: Radius of PNS
T: Temperature of PNS surface

GW

PNS

Frequency of GW tells us the evolution of PNS.

Why is Evolution of PNS important?
Hanke+13

PNS shrinks slowly.

↓,22

PNS shrinks fast.

↑,↑,↑The evolution of PNS is important gradient for theexplosion mechanism.

Origin of GW(2):SASI(Standing Accretion Shock Instability)(( ()))

100-200 Hz

SASI

GW

Due to SASI, the shock oscillate at 100-200Hz.
After that, PNS begins to oscillate at the same frequency.

From GW signals, we can get evidence of SASI

Summary of non rotating model

Frequency [Hz]Non rotating scenario
g-mode at PNS surface

1000

Prompt Convection

200100=> Evolution of PNS
PNS resonance of SASI

Nothing

0Explosion?

50100500 Time[ms]↑ Bounce time is determined by ν observation
24

Two typical cases
 Non rotating progenitor

Explosion Mechanism
2. GWs from 2D simulations
3. GWs from 3D simulations1.

 Rapidly rotating progenitor

GWs from Axisymmetric simulations
2. GWs from Non Axisymmetric simulations
1.

25

Typical Models in Axi-sym. sim.

26

Typical Models in Axi-sym. sim.

Bounce Signal at the rotational core-collapse
Rotation increase the GW amplitude until a limit.
27

Dimmelmeier+2008

Two typical cases
 Non rotating progenitor

Explosion Mechanism
2. GWs from 2D simulations
3. GWs from 3D simulations1.

 Rapidly rotating progenitor

GWs from Axisymmetric simulations
2. GWs from Non Axisymmetric simulations
1.

28

27.0M_s R2.029

Spiral Mode(ρ-<ρ>)/<ρ>(P-<P>)/<P>

300km

30

Rotational energy(T)/gravitational energy(W)reach some criteria => Spiral mode arises
In the rigid ball: 14%Ott+ 2005
In SNe case: ~ 6% (Called low-T/W instability)

Energy Transport by spiral mode
Energy Flux
with rapid rot.
wo rot.

Power ofνheating =10^52 erg/sPower of Spiralmode = 0.5 x
10^52 erg/s

EntropyRadius[km]31

Spiral mode transport energy from center to outerregion and helps explosion.

TOP

GW signals from rotating model
SIDE

SIDE

TOP

Takiwaki+ in prep

Bounce signal can be observed from side view.
Non-axisymmetric motion emits GWs at later phase.
32

TOP

Neutrino signals from rotating model

SIDE

Takiwaki+ in prep

Period of spiral mode is extracted by ν-signal
33

Feature of GWs from Rotational Explosion
Takiwaki+ in prep

Viewing from side direction

BounceOnly visible in side viewg-modeSpiral mode34

In addition to g-mode signal, GW from spiral mode arises
and spin period of PNS surface can be extracted.

Circular Polarization?
Hayama+2016=Data analysis=>
Circular Polarization Parameter, V

With the analysis we can extract circular polarizations.
We can distinguish Spiral mode from SASI-mode.
35

Summary of rotating model

Frequency [Hz]Rapidly rotating scenario

1000
200

Bounce signal(side view)g-mode at PNS surface=> Evolution of PNS

Low T/W instability=>Rotational Period100
050100Time[ms]↑ Bounce time is determined by ν observation
36

Summary
1. GW from SN gives the information on what happen

in the Fe core. Although the waveform iscomplicated, spectrogram gives hints on thephysical processes.
2. For non-rotating case, FOUR types of GWs isemitted.
From these, we can know the evolution of PNS andwhether strong SASI happens or not.
3. For rotating case, strong bounce signal is theevidence for the rotation. From the GWs, theinformation of spin period could be extracted.
37

Gravitational Wave Emission
in 3DGR Models
Comparison with sensitivitycurves(D=10kpc)