pmoesta@berkeley · superluminous lGRBs Core-collapse supernovae neutrinos turbulence Magnetic...

Philipp Mösta

Einstein fellow @ UC Berkeley [email protected]

NucAstro in the GW astronomy era ECT*, Trento Jun 13, 2017

The most powerful explosions in 3D

mailto:[email protected]?subject=

Philipp Mösta

Einstein fellow @ UC Berkeley [email protected]

NucAstro in the GW astronomy era ECT*, Trento Jun 13, 2017

Status of core-collapse supernova

simulations

mailto:[email protected]?subject=

3

~

Extreme core-collapse hyperenergetic superluminous lGRBs

Core-collapse supernovae neutrinos turbulence

Magnetic fields in high-energy astro

(Binary) black holes accretion disks EM counterparts

Binary neutron stars gravitational waves EM counterparts sGRBs

4

New era of transient science

Image: PTF/ZTF/COO Image: LSST

• Current (PTF, DeCAM, ASAS-SN) and upcoming wide-field time domain astronomy (ZTF, LSST, …) -> wealth of data

• adv LIGO / gravitational waves detected

• Computational tools at dawn of new exascale era

5

New era of transient science

Image: PTF/ZTF/COO Image: LSST

Transformative years ahead for our understanding of these events

• Current (PTF, DeCAM, ASAS-SN) and upcoming wide-field time domain astronomy (ZTF, LSST, …) -> wealth of data

• adv LIGO / gravitational waves detected

• Computational tools at dawn of new exascale era

6

Observational Facts

~5 per second in universe ~1 per day observed

large kinetic energies ~1051 erg

SN 1

987A

© A

nglo

-Aus

tral

ian

Obs

erva

tory

Progenitor BSG Sanduleak -69 220a, 18 MSUN

7

~

Astrophysics of core-collapse supernovae

Galaxy evolution/feedbackM82/Chandra/NASA

Heavy element nucleosynthesis

Birth sites of black holes / neutron stars Neutrinos

8

Red Supergiant Betelgeuse D ~200 pc

300 km

800 million km

HST

Central Engine”

- EM waves (optical/UV/X/Gamma): secondary information, late-time probes of engine

Observing core-collapse supernovae

9


300 km

800 million km

HST

Central Engine”

- Neutrinos - EM waves (optical/UV/X/Gamma):

secondary information, late-time probes of engine



10


300 km

800 million km

HST

Central Engine”

- Gravitational waves - Neutrinos - EM waves (optical/UV/X/Gamma):

secondary information, late-time probes of engine

Core-Collapse Supernova Energetics

11

• Collapse to a neutron star: 3 x 1053 erg = 300 [B]ethe gravitational energy (≈0.15 MSunc2) released. Initially stored in protoneutron star. -> Any explosion mechanism must tap this reservoir.

•1051 erg = 1 B kinetic and internal energy of the ejecta. (Extreme cases: 10 B; hyperenergetic supernova)

•99% of the energy is radiated in neutrinos over tens of seconds in protoneutron star cooling.->Strong evidence from SN 1987A neutrino observations.

SN 1987A: Neutrino Detection

12

13

Gas/plasma dynamicsMagneto-Hydrodynamics

A multiphysics challenge

14

Gas/plasma dynamics

Gravity

Magneto-Hydrodynamics

General Relativity


Figure: C. Reisswig

ADM 3+1 split of spacetime

3-hyper-surface

• 12 first-order hyperbolic evolution equations • 4 elliptic constraint equations • 4 coordinate gauge degrees of freedom: α, βi

Dynamical gravity / Numerical Relativity

15

Gµ =8G

c4Tµ

Tim

e

Figure: C. Reisswig

ADM 3+1 split of spacetime

3-hyper-surface

Dynamical gravity / Numerical Relativity

16

• Required for black hole collapse and gravitational waves!

Tim

e

17

Gas/plasma dynamics

Nuclear EOS, nuclear reactions & ν interactions

Gravity


Nuclear and Neutrino Physics

General Relativity


18

Gas/plasma dynamics


Gravity

Neutrino transport



General Relativity

Boltzmann Transport Theory


19

Gas/plasma dynamics


Gravity

Neutrino transportFully

cou

pled

!



General Relativity


All four forces!


20



General Relativity



Neutrino transportFully

cou

pled

!

Additional Complication: Core-Collapse Supernovae are 3D

• rotation • fluid and MHD instabilities, multi-D structure, spatial scales

Need 21st century tools: • cutting edge numerical algorithms • sophisticated open-source software infrastructure • peta/exa scale computers

All four forces!

A multiphysics challengeGas/plasma dynamics

Gravity

Core collapse basics

21

up to

[not drawn to scale]

Fe-group nucleiSi

O/Ne/MG

C

8M . M . 130M

[not drawn to scale]

22

2000km

Protoneutron star r~30km

Iron core

Nuclear equation of state stiffens at nuclear density

Inner core (~0.5 ) -> protoneutron star + shockwave

M

2000km


23

2000km

Outer core accretes ontoshock & protoneutron star with O(1) /s

Shock stalls at ~ 100 km

Reviews:Bethe’90 Janka+‘12


Iron core

M

2000km Nuclear equation of state stiffens at nuclear density


M


accretion

L

shock

The Core-Collapse Supernova Problem

The shock always stalls:

• Dissociation of Fe-group nuclei @ ~8.8 MeV/baryon (~17 B/MSun).

• Neutrino losses initially @ >100 B/s (1 [B]ethe = 1051 ergs).

24

Hans Bethe 1906-2005

~

25

2000km

Core-collapse supernova problem: How to revive the shockwave?


accretion

L

shock


Iron core



M


26

2000km

Engine formation?


accretion

L

shock


Iron core



M


27

2000km

accretion

L

shock

2000km

Core collapse basicsNeutrino mechanism

28

2000km

accretion

L

shock

2000km


29

2000km

accretion

L

shock

2000km


Theory incomplete!

30

2000km2000km

Roberts+16

3D Volume Visualization of

Entropy


Neutrino Mechanism

Ott+ ’08

31

Cooling:

Heating via charged-current absorption:

Bethe & Wilson ’85; also see: Janka ‘01, Janka+ ’07

30 km 60 km 120 km 240 kmNeutrino radiation field:

Heating efficiency:

32

Frontiers in neutrino mechanism

Key for explosion:

compactness

turbulence

SASI

Janka+16

Takiwaki+16


Does rotation help?

34


Current frontiers:

turbulence detailed neutrino transport numerical resolution progenitor burning

Radice+15

Couch+15

Erik’s talk for details!

Discuss!

35

2000km2000km

Obergaulinger+14

Very high magnetic field in non-rotating progenitors can aid explosion (in 2D)

Convection/SASI can amplify field at fixed amplification factor

Most models explode as hydro!


Hypernovae & GRBs

36http://apod.nasa.gov/apod/ap000628.html

Hypernovae & GRBs

37

• But not all stripped-envelope supernovae come with GRBs

• Trace low metallicity environments

• 11 long GRB – core-collapse supernova associations.

• All GRB-SNe are stripped envelope, show outflows v~0.1c

Neutrino mechanism is inefficient; can’t deliver a hypernova

38

Superluminous supernovae

Some events: stripped envelope no interaction

Gal-Yam+12

Elum ~ 1045 erg Erad up to 1052 erg

39

Lunnan+14

Connection between SLSN Ic and lGRBs • prefer star-forming galaxies • low metallicity • large core angular momentum !?

Superluminous supernovae

Greiner+15

Common engine? Magnetar?

40

Superluminous / hyperenergetic supernovae

SLSN Ic SN Ic-bl lGRBs

Common engine? Magnetar?

41

Superluminous / hyperenergetic supernovae

SLSN Ic SN Ic-bl lGRBs

FRBs

Protomagnetar powered explosions

42

Rapid Rotation + B-field amplification

2D: Energetic bipolar explosions Energy in rotation up to 1052 erg

Results in ms-period proto-magnetar

Protomagnetar powered explosions

Obergaulinger+17

2D: Diversity of outcomes depending on rotation rate/progenitor profile

44Octant Symmetry (no odd modes) identical to 2D Full 3D

! 2000 km " ! 2000 km "

3D explosions dynamics very different!PM+ 14

What’s going on here?

45

• m=1 spiral instability • consistent with MHD kink instability;

should hold independent of initial B-field strength

H (Btor )

5 10 15 20 25105

104

103

102

101

1

t tbounce [ms]

r[k

m]

magnetic pressure b2/2

zi = 30 kmzi = 44 kmzi = 59 kmzi = 74 kmet/t , t = 1.4 ms

zi = 30 kmzi = 44 kmzi = 59 kmzi = 74 kmet/t , t = 1.4 ms

fgm

4a

p

Btor

1ms

fgm

4aBz

Btor

5km

PM, Richers+ 14with Sherwood Richers (Caltech)

46

• B-field near proto-NS: Btor >> Bz

• Unstable to MHD screw-pinch kink instability.

• Similar to situation in Tokamak fusion reactors!

Braithwaite+ ’06

Credit: Moser & Bellan, CaltechSarff+13

MHD Kink Instability

3D Volume Visualization of

47

EntropyPM+ 14

dual-lobe ‘slow’ explosion

48

PM+ 17 (in prep.)

180 200 220 240 260 280800

900

1000

1100

1200

1300

1400

t tbounce [ms]

r[k

m]

Continued accretion -> Black hole engine possible!

Implications for long Gamma-Ray Bursts

Jet-driven explosions proposed as site for r-process

49

Neutron-rich nucleosynthesis in supernovae Creating the heaviest elements

• Low electron fraction

• Medium entropy • Low density • High

temperature

Sneden+ 08

50

R-process: First results

PM, Roberts+ 17 (in prep)Halevi, PM, Roberts+ 17 (in prep)

51

Winteler+12

Nishimura+15

R-process in jet-driven supernovae

Robust r-process in 2D simulations for prompt explosions!

52


Halevi, PM 17 (in prep)

B = 1013 G

53


80 100 120 140 160 180 2001016

1014

1012

1010

108

106

104

102

100

mass number A

Mej

ecta

[M]

L = 0L = 1051 erg/sL = 1052 erg/sL = 1053 erg/s


80 100 120 140 160 180 2001016

1014

1012

1010

108

106

104

102

100

mass number A

Mej

ecta

[M]



PM, Roberts, Halevi+ 17 (in prep)

B = 1012 G / octant

B = 1012 G full 3D

54

Gravitational waves from rotating core collapse

Fuller+15

Richers+17

Gravitational waves from rotating core collapse

Gossan+16

see Jade’s talk later in afternoon

Magnetorotational Mechanism

56Burrows+’07

Caveats:

1) Need high core spin; only in very few progenitor stars?

2) Magnetic field amplification?

57Burrows+’07

Caveats:

1) Need high core spin; only in very few progenitor stars?

• chemically homogenous evolution • binary interactions • but angular momentum loss due to

magnetic braking or mass loss?

Likely rare but can work outBurrows+’07


58

Caveats:

2) Magnetic field amplification?

• Progenitor magnetic field strength expected no stronger than 10^9/10^10 G • Need > 10^15 G after core bounce • Flux compression and winding only

yield factor 10^3 amplification

At least another factor 10^3 missing!Burrows+’07


59

One proposed channel: MRI + dynamo

MC Mi Mo

60

Stability criterion:

[Balbus&Hawley 91,98, Akiyama+03, Obergaulinger+09]

What’s the situation in core-collapse?

82 < !2BV + r

d2

dr< 0

Magnetic field amplificationMRI activated locally Akiyama+03, Shibata+06, …

M. Obergaulinger et al.: MRI in core collapse supernovae 259

Fig. 22. Volume rendered magnetic field strength of a model with bz0 = 4 × 1013 G computed in a box of 1 × 2 × 1 km3 with a resolution of 20 m at

t = 21.5 ms (left) and t = 37.2 ms (right), respectively. The coordinate directions are indicated as in Fig. 19.

the weakest initial field, because the theoretical growth rate forthe fastest growing MRI mode is σMRI = 1.14 ms−1 for thesemodels (see Sect. 4.2.1).

To investigate the stability properties of large-scale channelmodes as a function of the box geometry, we simulated mod-els with an initially uniform magnetic field using boxes of dif-ferent size and shape. The models were rotating according toΩ0 = 1900 s−1 and αΩ = −1.25, and their initial magneticfield was bz

0 = 4 × 1013 G when applying velocity dampingboundaries, and bz

0 = 2 × 1013 G otherwise. We varied boththe ratio between the radial and vertical, Lϖ/Lz, and the radialand toroidal size, Lφ/Lϖ, size of the box. The grid resolutionwas 20 m (see Table B.3). Plotting the stress ratios Mmax

ϖφ /Mtermϖφ

(Fig. 23; damping boundaries) and ⟨Mϖφ⟩/Mtermϖφ (Fig. 24; non-

damping boundaries) as a function of the aspect ratio of the com-putational box, provides some indication of the range of Mϖφvalues prevailing during the post-growth phase. The ratios al-low one to distinguish models with a strong variability due tothe dominant re-appearance of channel modes from those mod-els exhibiting a smooth evolution without dominant large-scalecoherent structures.

We find that models with a radial aspect ratio Lϖ/Lz = 1and a toroidal aspect ratio Lφ/Lz ≥ 2 are unstable against par-asitic instabilities, independent of the grid resolution in toroidaldirection. Turbulence develops and leads to a flow structure asshown in Fig. 22. Models having the same radial aspect ratio,but a smaller toroidal one are stable and evolve similarly as ax-isymmetric models, i.e., parasitic instabilities do not grow anda dominant large-scale channel flow develops, which gives riseto a morphology of the type presented in Fig. 22. These find-ings do not depend on how the growth of the MRI ends, i.e.,whether velocity damping is applied and reconnection betweenadjacent channels occurs inside the box, or whether no damp-ing is imposed and reconnection occurs near the surface of thecomputational box.

These results can be understood from the analysis of par-asitic instabilities by Goodman & Xu (1994), who argued thatthree-dimensional flows are unstable against parasitic instabili-ties, but these instabilities can be suppressed by the geometry ofthe computational box. According to their analysis, the growthrate of the parasitic instabilities is highest for modes with halfthe wave number of the unstable MRI modes they are feeding

1log Lϖ / Lz

1

log

Lφ /

Lz

log Mϖφmax / Mϖφ

term

0 0.75 1.50 2.25 3

1log Lϖ / Lz

log Mϖφavge / Mϖφ

term

−0.25 0.25 0.75 1.25 1.75 2.25

Fig. 23. The left panel shows the ratio of the maximum Maxwell stressper unit volume, Mmax

ϖφ , and its value at MRI termination, Mtermϖφ , as a

function of the toroidal and radial aspect ratios, Lφ/Lz and Lϖ/Lz forthe models listed in Table B.3. The right panel shows the ratio of Mϖφaveraged over the saturation phase and the value at MRI termination.Each model is represented by a symbol its color reflecting its maximumMaxwell stress. All models are computed imposing velocity dampingat the radial grid boundaries.

off. Hence, if a channel flow forms at late times with a wave-length equal to the box size in z-direction, Lz, unstable parasiticmodes must have a toroidal wavelength ∼2Lz to grow rapidly.Thus results in the criterion for the channel flow instability wehave found in our simulations.

In accordance with simulations presented recently by Bodoet al. (2008), we find that models with a radial aspect ratioLϖ/Lz ≤ 1 experience a second exponential growth phase asdescribed in Sect. 4.2 (note the large ratios of Mmax

ϖφ and Mtermϖφ

for the corresponding models in Fig. 23), whereas a larger ra-dial aspect ratio appears to favor a less violent post-growth phasewhere coherent channel modes can appear but are disrupted aftera short time. Bodo et al. (2008) obtained this result for simula-tions performed with a toroidal aspect ratio Lφ/Lz = 4.

Obergaulinger+09

Saturation strength? Secondary instabilities, neutrino viscosity and drag Guilet+15, Rembiasz+16, …

Rembiasz+16

Global 2D studies Sawai+13,14, …

Guilet+15

62

First global 3D MHD turbulence simulations

Do MRI and dynamo build up dynamically relevant global field?

• 10 billion grid points (Millenium simulation used 10 billion particles)

• 130 thousand cores on Blue Waters

• 2 weeks wall time

• 60 million compute hours

• 10000 more expensive than any previous simulations

PM+ 15 Nature

63

3D magnetic field structure

dx=500m dx=50mdx=200m dx=100m

PM+ 15 Nature

64

PM+15 Nature

65

Growth at Large Scales

saturation within 60ms

0 5 10

1

2

3

4

5

6

7

t tmap [ms]

E k,m

ag(t

)[1

033er

g]

(2.05 + 0.75 ms1 · (t tmap)) · 1033

5 · 1032 e(ttmap)/t, t = 3.5 msk = 4k = 6k = 8k = 10k = 20k = 50k = 100

(2.05 + 0.75 ms1 · (t tmap)) · 1033

5 · 1032 e(ttmap)/t, t = 3.5 msk = 4k = 6k = 8k = 10k = 20k = 50k = 100

PM+15 Nature

66

Global Field Structure

t=0ms

dx=500m dx=50m

t=10ms t=10msPM+15 Nature

67

Global Field Structure

t=0ms

dx=500m dx=50m

t=10ms t=10ms

Magnetar formation?

PM+15 Nature

68

From simulations to observationsState of the art now:

Current frontier:

Detailed simulations full physics 0.1-1s inner core ~10000km

PM, Tchekhovskoy 17 (in prep)

Full 3D, full physics

Full star

1) Engine model from full-physics simulations 2) Simplified simulations with engine model to shock breakout

69

From simulations to observationsState of the art now:

Current frontier:


Squire, PM, Lecoanet 17 (in prep)


0 5 10 15 20 25

-20

-10

0

10

20

-5.0×10-7

5.0×10-7

1.5×10-6

2.5×10-6

Daedalus simulationGet mean fields from 3D sim

70

From simulations to observationsState of the art now: Future:

Full-star simulations full physics shock breakout

detailed light curves detailed spectra connect observations and engines map progenitor params


Current frontier:


71

Summary3D explosion dynamics matter for neutrino-driven

and GRB-SN; details need to be worked out

Very important to work out multimessenger signatures; sensitive to nuclear/neutrino physics

Need subgrid (or similar models) to capture relevant dynamics from high-resolution simulations

3D hybrid simulations to predict observable signatures reliably

72

Thank you!

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