ニュートリノで解き明かす
大質量星の重力崩壊
Shunsaku Horiuchi
Virginia Tech

Image credit: NASA/ESAOutline
Opportunities with Galactic supernovae: transient(a selection)
Beyond the Milky Way: diffuse
Multi-messenger connections
Concluding remarks

Shunsaku Horiuchi (Virginia Tech)2

Collapse of massive stars
Massive (>8Msun) star structure

H He C O Si

Core collapse(implosion)
Explosion

Fe

R: 8000 km à ~20 km
r: ~109 g cm-3 à ~1014 g cm-3
T: ~1010 K à ~30 MeV
Shunsaku Horiuchi (Virginia Tech)

Adapted from slides by G. Raffelt 3

The explosion mechanismExplosion mechanism
The bounce shock stalls – and must be
energetically revived.

nngitaheThe prevailing mechanism is turbulenceenhanced energy deposition• 1D: fails• 2D: many successful explosions• 3D: success, but fewer simulations

Neutrino luminosity

Neutrino mechanism
The neutrinos achieve this:ionter
ccass
MaVS

Explosions

Critical curve

Explosion failure andblack hole formation

Mass accretion rate

Many groups: Australia, Germany, Japan, US
Shunsaku Horiuchi (Virginia Tech)

4Neutrino heating mechanismsFor mass < 10 Msun

For mass < 15 Msun

For mass < 40 Msun

Can neutrinos reveal the progenitor Mdot?
Can neutrinos reveal the explosion mechanism?

9.6 Msun, Melson et al 2015,11.2 Msun, Takiwaki et al 2014

20 Msun, Melson et al 2015

Readily explodes byneutrino heating,even in sphericalsymmetry.

Does not explode in
spherical symmetry,but does explode inaxisymmetric and infull 3D via convection

Does not explode in
spherical symmetry,but does explode inaxisymmetric and infull 3D with SASI

Kitaura et al 2006

Shunsaku Horiuchi (Virginia Tech)

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Neutrinos: highlights
Three main phases of supernova neutrino emission:

BurstAccretion

CoolingCore collapse timing

Explosion mechanism

Proto-neutron star info

Supernova triangulation

Progenitor information

Exotic energy loss

Standard candle

Supernova pointing

Nucleosynthesis

Oscillations may be simple

Collective oscillations

Shock effects

Neutrino mass ordering…

Nuclear physics…
Shunsaku Horiuchi (Virginia Tech)…
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Progenitor dependenceCore density profile:
Progenitor core density profile
critical for collapse evolution

MassM/M⇠M =R(Mbary = M)/1000 km t
O’Connor & Ott (2011)

ionteracc

VS !
truNeeathoniing

Compactness:
A simple way to capture thedensity structure• Higher x à higher Mdot
• Lower x à lower Mdot
Shunsaku Horiuchi (Virginia Tech)

Hig

herx

Lower&M
dox&Mdott7

Accretion phase: progenitor information
Progenitor dependence:
The neutrino emission reflects the compactness of the progenitor
Spherical simulationsèèèAxisymmetric simulations(d=10 kpc)

Shunsaku Horiuchi (Virginia Tech)

O’Connor & Ott (2013)

Horiuchi et al (2017)8Accretion phase: SASI-driven explosion?
Signatures:• SASI’s time variations (~10-20 ms)
get imprinted on the neutrino
luminosity and energy.
• Can be measured with large
volume detectors

spiralSloshing(d=10 kpc)

Multiple SASI
episodes + convection

Single SASI episode+ convection

No SASI episode,only convection

Shunsaku Horiuchi (Virginia Tech) Tamborra et al (2013, 2014), based on Hanke et al (2013) see also Lund et al (2010, 2012)9Cooling phase
Late-time signal
Detectable up to O(100) seconds post bounce
Depends sensitively on the proto-neutron star mass(d=10 kpc)

2.05
Msunsun
5M
1.3

unMs
1.2

Shunsaku Horiuchi (Virginia Tech)

Suwa et al (2019)10

Did it collapse to a black hole?
Moment of black hole formation
Neutrinos light curve can reveal the
moment of black hole formation

BH caseHigh event rates predictedTermination(but not to 0)
NS caseO’Connor (2015)
Liebendoerfer et al (2004)
Shunsaku Horiuchi (Virginia Tech)

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Distance, strategy, physics!
Nn >> 1 : BURST

Nn ~ 1 : MINI-BURST

Nn << 1 : DIFFUSE

SN rate ~ 0.01 /yr

SN rate ~ 0.5 /yr

SN rate ~ 108 /yr~kpc

Physics
reach~Mpc~Gpc

Adapted from Beacom (2012)

Galactic burst

Mini-bursts

Diffuse signal

Multi-messenger
astronomy, explosion
mechanism, neutrino
physics

supernova
variety

Average emission, multi-populations(e.g., black holes)

reviews by Beacom (2010), Lunardini (2010)
Shunsaku Horiuchi (Virginia Tech)

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Landscape of supernova diversity
Systematic studies:

Shunsaku Horiuchi (Virginia Tech)• Based on “neutrino engine” 1D simulation suite• Characterizing in ZAMS mass looks incomplete

Janka 2017; based on Ertl et al (2016); see also Ugliano et al (2012),Sukhbold et al (2016), Pejcha & Thompson (2015), Mueller et al (2016)13

Making sense of the landscape
Failure should correlate with high compactness
Failed explosions correspond to stars with large compactness
Red: explosions

M/M⇠M =R(Mbary = M)/1000 km t

Gray: failed explosions•••

BH formation for x2.5 > 0.25
Explosions for x2.5 < 0.15
Mixture in between

Compactness has surprising predictability:• 1 compactness successful in up to ~88% of stars• 2 parameters up to ~97% of stars
Shunsaku Horiuchi (Virginia Tech)

Erlt et al (2015), Pejcha & Thompson (2015)14

Red supergiant problem
Pre-imaging:
Limited to nearby
SNe, highly
successful

A deficit of high mass supernova progenitors Kochanek et al (2008)
Sample: volume limited to < 28 Mpc (V<2000 km/s)
Known red-supergiants (@MW, LMC)

Observed progenitors

D ~ 4 Mpc
pre-image by HST

Log L/Lsun

SN 2008bk

è Highest luminosity RSGs missing
from progenitor sample

Shunsaku Horiuchi (Virginia Tech)

Smartt (2009), Smartt (2015)15

Red supergiant problem
Supergiants may not be exploding• Missing RSG mass ~16 –25 Msun
• Similar to high compactness stars least likely to explode(Other explanations have been explored)
Horiuchi et al (2014); Kochanek (2014)
0.5

Missing RSG
x2.5

0.4
0.3
0.2

xcrit

0.1
0102030 40 50 60 70 80 100
initial mass [Msun]

0.5

Compactness peak related to core C
SN rate problem
a = -2.15
0.4
burning transition.
a = -2.35
a = -2.55• 0.3Exact position depends on nuclear
reaction rates, e.g., 12C(a,g)16xcritO.
0.2x2.5•

Smartt et al (2009)
Shunsaku Horiuchi (Virginia Tech)

0.1
016

Explosions & implosions
Direct searchcandidate

Theory:(2-parametercriterion)
Sukhbold & Adams (2019)

è Failed explosion may not be rare. Fraction can be 10–40% of all core collapse
Shunsaku Horiuchi (Virginia Tech)17

Average neutrino flux
Average neutrino emission• Use 100+ simulations to characterize progenitor dependence• Use initial mass function to distribute progenitors• Include collapse to black holes, characterized by critical compactness

dN / dE [/MeV]

ne56

1045% BH
0% BH

x2.5,crit = 0.1
x2.5,crit = 0.2x2.5,crit = 0.3x2.5,crit = 0.4

more BH

55

1054

10 0e.g., papers by Fischer et al, Sumiyoshi et al,
Nakazato et al, O’Connor & Ott, …

Shunsaku Horiuchi (Virginia Tech)

5

10 15 20 25 30 35 40 45 50

E [MeV]

Horiuchi et al (2018)18

Backgrounds and search window
Optimal search window• With water: background dominated search.
• Invisible muons: large background
Signal+⌫¯e + p ! e + n

Invisiblemuons

Shunsaku Horiuchi (Virginia Tech)

Super-K (2012)19

Super-K with Gadolinium
Background rejection:
Signal produces a neutron, while manybackgrounds do not

Beacom & Vagins (2004)+⌫¯e + p ! e + n
w/out Gd

Capture on protons,
signal mostly lost(~18% tagging)with Gd

Capture on Gadolinium,
yields a coincidence
signal (~90% tagging)

EGADS: Evaluating Gadolinium’s
Action on Detector Systems

Approved in 2015
Infrastructure upgrades complete
Gd will be added in phases from 2019/2020
Shunsaku Horiuchi (Virginia Tech)

DT ~ 30 µs, Dl ~ 50 cm

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Backgrounds and search window
Optimal search window• Invisible muons: largely reduced• Gadolinium opens a signal-dominated window ~10-30 MeV

Shunsaku Horiuchi (Virginia Tech)

Super-K (2012)

Beacom & Vagins (2004)21

Upcoming sensitivities
SuperK + Gd
Average emission parameters frommulti-D sims similar to “D”

SpectrumSK + Gd (>10MeV) [/yr]4 MeV

1.8 +/- 0.5

4 MeV+BH(30%)~ 2.5SN1987A

1.7 +/- 0.5••Sensitive to BHs
Sensitive to core collapse history(à tests of star formation history)
More BH(5 years)

Shunsaku Horiuchi (Virginia Tech)

fBH~0.2

Yuksel et al (2006)

~0.05

~0.03

Horiuchi et al (2018); Lunardini (2009), Lien et al(2010), Yuksel & Kistler (2015), Moller et al (2018)22

MULTI-MESSENGER CONNECTIONS

Shunsaku Horiuchi (Virginia Tech)

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The next Galactic supernova

LIGO
ASAS-SN

VIRGO
Palomar

SubaruKAGRA
LSST+ CR

Super-K

Shunsaku Horiuchi (Virginia Tech)

JUNO

DUNE

Nakamura,Hyper-Kamiokande
Horiuchi et al (2016)24

Neutrino confidence

Running

Reveal IF: High number statistics expected from a Galactic core collapse

Not shown: direct dark matter detectors

Shunsaku Horiuchi (Virginia Tech)

Mirizzi et al (2015); Scholberg (2012)25

Alerting the community
Neutrinos: rapid sharing of core collapse occurrenceü SNEWS:
Borexino
DayaBay
HALO
IceCubeKamLAND
LVD
Super-K

http://snews.bnl.gov
astro-ph/0406214

Coincidence server (@BNL)

ü Individual detectors• EGADS: automated alert within ~ 1 s• Super-K: alert within ~ 1 hour of neutrino burst(info: time, duration, total events, pointing)

Rapid ALERTs
Email, IAU, Atel, GCNe.g., Adams et al (2013)
Shunsaku Horiuchi (Virginia Tech)

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Multi-messenger: electromagnetic1day

à days delay, hours duration
à minutes delay, seconds duration

1hr

Shock breakout (SBO) timescales:• For RSG (=type IIP): 1000 Rsun, 10 Msun
• For WR (=type Ibc): 1 Rsun, 1-10 Msun

Li et al (2010)

à Rapid alert will help chasethe shock breakout signal
Kistler et al (2013)
based on Matzner & McKee (1999)
Shunsaku Horiuchi (Virginia Tech)

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Pointing
POINTING to core collapse
Use e- scattering in the forward cone:~300 events at SK⌫+e !⌫+e

Background mostly due to IBD⌫¯e + p ! e+ + n
Water only

Super-K

Hyper-K~6 deg~1.4 deg

Beacom & Vogel (1999), Tomas et al (2003)

Shunsaku Horiuchi (Virginia Tech)28

Pointing
POINTING to core collapse
Use e- scattering in the forward cone:~300 events at SK⌫+e !⌫+e

Background to be reduced by neutron
tagging with Gd (~90% efficiency):⌫¯e + p ! e+ + n

Remaining background is the ~10% of
IBD and ne absorption on 16O (~20-80events)
à Pointing accuracyof several degrees

Shunsaku Horiuchi (Virginia Tech)

Super-K

Hyper-K

Water only

~6 deg~1.4 deg

Water + Gd (90% tag)~3 deg~0.6 deg

Beacom & Vogel (1999), Tomas et al (2003)

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Multi-messenger: electromagnetic
Important WHERE supernova occurs:
The ~35%MilkyareWay
putsreachsevereattenuation in the optical regime (not so much in IR)
withinof large
FOV <1m class telescopes
Us~20% will need need >1mclass telescopes – helped byGd pointing improvement

Nakamura, Horiuchi et al (2016)
Shunsaku Horiuchi (Virginia Tech)

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SNEWS2.0: Triangulation
SK+JUNO+DUNE

Coordinated pointing:Automate triangulation into upgraded
SNEWS2.0 alerts
HK+JUNO+DUNE +IceCube

HK+JUNO+DUNE

Linzer & Scholberg (2019);
See also, Brdar et al (2018),
Beacom & Vogel (1999),
Mhlbeier et al (2013),

Shunsaku Horiuchi (Virginia Tech)

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Timing & Gravitational waves
1000

e.g., IceCube: bounce time can be estimatedto within ±3.5 ms at 95 % C.L. Halzen & Raffelt (2009)

Frequency [Hz]WHEN one should look:

WITHOUT neutrino timing
800 S/N ~ 3.54600

2.5

3.5
32400

1.5
1200
0.50500

Time [ms]1000500450

Frequency [Hz]400

à Timing of core bounce helps GW detection
Shunsaku Horiuchi (Virginia Tech)

Nakamura, Horiuchi et al (2016)

WITH neutrino timing
S/N ~ 7

76350

5300
4250
200

3150

2100

18.5 kpc

50
10203040
Time [ms]506032

Concluding remarks: future decades
Theory:multiple detailed
3D hydrodynamic
and oscillation
simulations

Optical:high cadence telescopesGravitational wave:
Global network of
GW detectors

Neutrinos:rich data frompresent and future
detectors,
comparison withdiffuse backgroundShunsaku Horiuchi (Virginia Tech)

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Shunsaku Horiuchi (Virginia Tech)

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SN2011dhdeficit

V-bandR-bandGerke et al. (2015)

Results so far:In 7 years running,• 6 luminous CC supernovae (09dh,11dh, 12fh, 13ej, 03em, 14bc)• 1 candidate failed supernova:
NGC6946-BH1 (@~6Mpc); SED well fit
by 25Msun RSG

è Failed fraction
Shunsaku Horiuchi (Virginia Tech)

With the candidate(90%CL)
Adams et al (2016)37

Time-integrated neutrino signal
Spectrum per core collapse
Spectral parameters show systematicCollapse to black hole speeds up withdependence on progenitor compactness higher compactness

Horiuchi et al (2018)

Shunsaku Horiuchi (Virginia Tech)

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The challenge: beating backgroundTwo approaches :1. Neutrino trigger: look for doublets or higher multiplets,depending on bkg rate:• Atmospheric neutrinos• Invisible muon decays• Spallation daughter decays
e.g., doublets in 10 sec occurs once per ~10 years (scaling SK-II to 0.56 Mton)
2. EM trigger: use SBO or early SN light curve to model constrain the bounce timee.g., Cowen et al (2009)

e.g., background rate in signal region is ~0.8 /day/0.56Mton (scaling from SK-II)à maybe even can use neutrino singlets
H2O only

H2O + GdSearch energy window [MeV]

18-30

12-38

Signal n (in 10 sec, d = 1 Mpc, 0.56Mton)~5~10Background n (over 1 day, 0.56Mton)~0.8~1.1

Shunsaku Horiuchi (Virginia Tech)

Ando et al (2005)

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