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 Core collapse (implosion) Massive (>8Msun) star structure Explosion Fe H He Si C O R: 8000 km à ~ 20 km r : ~ 10 9 g cm -3 à ~ 10 14 g cm -3 T: ~ 10 10 K à ~ 30 MeV Adapted from slides by G. Raffelt Shunsaku Horiuchi (Virginia Tech) 3
The explosion mechanism Explosion mechanism The bounce shock stalls – and must be Critical curve energetically revived. Explosions Neutrino mechanism Neutrino luminosity The neutrinos achieve this: Mass accretion VS n heating Explosion failure and black hole formation The prevailing mechanism is turbulence- enhanced energy deposition 1D: fails • Mass accretion rate 2D: many successful explosions • 3D: success, but fewer simulations • Many groups: Australia, Germany, Japan, US Shunsaku Horiuchi (Virginia Tech) 4
Neutrino heating mechanisms For 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 Kitaura et al 2006 Readily explodes by Does not explode in Does not explode in neutrino heating, spherical symmetry, spherical symmetry, even in spherical but does explode in but does explode in symmetry. axisymmetric and in axisymmetric and in full 3D via convection full 3D with SASI Shunsaku Horiuchi (Virginia Tech) 5
Neutrinos: highlights Three main phases of supernova neutrino emission: Burst Accretion Cooling Core 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) 6
Progenitor dependence Core density profile: � M/M � Progenitor core density profile � ξ M = critical for collapse evolution � R ( M bary = M ) / 1000 km � t O’Connor & Ott (2011) Mass accretion Higher x & Mdot Neutrino heating VS ! Compactness: L o w e A simple way to capture the r x & density structure M d o t • Higher x à higher Mdot • Lower x à lower Mdot Shunsaku Horiuchi (Virginia Tech) 7
Accretion phase: progenitor information Progenitor dependence: The neutrino emission reflects the compactness of the progenitor Spherical simulations èèè Axisymmetric simulations (d=10 kpc) O’Connor & Ott (2013) Horiuchi et al (2017) Shunsaku Horiuchi (Virginia Tech) 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 spiral Sloshing (d=10 kpc) Multiple SASI Single SASI episode No SASI episode, episodes + convection + convection only convection Tamborra et al (2013, 2014), based on Hanke et al (2013) see also Lund et al (2010, 2012) Shunsaku Horiuchi (Virginia Tech) 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) 2.05Msun 1.35Msun 1 . 2 M s u n Suwa et al (2019) Shunsaku Horiuchi (Virginia Tech) 10
Did it collapse to a black hole? Moment of black hole formation Neutrinos light curve can reveal the moment of black hole formation High event rates predicted Termination (but not to 0) BH case NS case O’Connor (2015) Liebendoerfer et al (2004) Shunsaku Horiuchi (Virginia Tech) 11
Distance, strategy, physics! N n >> 1 : BURST N n ~ 1 : MINI-BURST N n << 1 : DIFFUSE SN rate ~ 10 8 /yr SN rate ~ 0.01 /yr SN rate ~ 0.5 /yr ~ kpc ~ Mpc ~ Gpc Adapted from Beacom (2012) Galactic burst Mini-bursts Diffuse signal Physics Multi-messenger supernova Average emission, multi-populations reach astronomy, explosion variety (e.g., black holes) mechanism, neutrino physics reviews by Beacom (2010), Lunardini (2010) Shunsaku Horiuchi (Virginia Tech) 12
Landscape of supernova diversity Systematic studies: • 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), Shunsaku Horiuchi (Virginia Tech) 13 Sukhbold et al (2016), Pejcha & Thompson (2015), Mueller et al (2016)
Making sense of the landscape Failure should correlate with high compactness Failed explosions correspond to stars with large compactness Gray: failed explosions Red: explosions � BH formation for x 2.5 > 0.25 M/M � • � ξ M = Explosions for x 2.5 < 0.15 • � R ( M bary = M ) / 1000 km Mixture in between • � t Compactness has surprising predictability: • 1 compactness successful in up to ~ 88% of stars • 2 parameters up to ~ 97% of stars Erlt et al (2015), Pejcha & Thompson (2015) Shunsaku Horiuchi (Virginia Tech) 14
Red supergiant problem Pre-imaging: A deficit of high mass supernova progenitors Kochanek et al (2008) Limited to nearby Sample: volume limited to < 28 Mpc (V<2000 km/s) SNe, highly Known red-supergiants (@MW, LMC) Observed progenitors successful SN 2008bk D ~ 4 Mpc Log L/Lsun pre-image by HST è Highest luminosity RSGs missing from progenitor sample Smartt (2009), Smartt (2015) Shunsaku Horiuchi (Virginia Tech) 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 0.4 0.3 x 2.5 x crit 0.2 0.1 0 10 20 30 40 50 60 70 80 100 initial mass [Msun] 0.5 Compactness peak related to core C • burning transition. Exact position depends on nuclear • reaction rates, e.g., 12 C( a , g ) 16 O. Smartt et al (2009) Shunsaku Horiuchi (Virginia Tech) 16
Explosions & implosions Direct search candidate Theory: (2-parameter criterion) 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 • 45% BH x 2.5,crit = 0.1 n e x 2.5,crit = 0.2 x 2.5,crit = 0.3 56 dN / dE [/MeV] 10 0% BH x 2.5,crit = 0.4 more BH 55 10 54 10 0 5 10 15 20 25 30 35 40 45 50 E [MeV] e.g., papers by Fischer et al, Sumiyoshi et al, Nakazato et al, O’Connor & Ott, … Horiuchi et al (2018) Shunsaku Horiuchi (Virginia Tech) 18
Backgrounds and search window Optimal search window With water: background dominated search. • Invisible muons: large background • ν e + p → e + + n ¯ Signal Invisible muons Super-K (2012) Shunsaku Horiuchi (Virginia Tech) 19
Super-K with Gadolinium Background rejection: Signal produces a neutron, while many backgrounds do not Beacom & Vagins (2004) ν e + p → e + + n ¯ w/out Gd with Gd EGADS: Evaluating Gadolinium’s Action on Detector Systems Capture on protons, Capture on Gadolinium, signal mostly lost yields a coincidence ( ~ 18% tagging) signal ( ~ 90% tagging) Approved in 2015 Infrastructure upgrades complete Gd will be added in phases from 2019/2020 D T ~ 30 µ s, D l ~ 50 cm Shunsaku Horiuchi (Virginia Tech) 20
Backgrounds and search window Optimal search window Invisible muons: largely reduced • Gadolinium opens a signal-dominated window ~ 10-30 MeV • Beacom & Vagins (2004) Super-K (2012) Shunsaku Horiuchi (Virginia Tech) 21
Upcoming sensitivities SuperK + Gd Spectrum SK + Gd (>10MeV) [/yr] Average emission parameters from 4 MeV 1.8 +/- 0.5 multi-D sims similar to “D” 4 MeV+BH(30%) ~ 2.5 SN1987A 1.7 +/- 0.5 Sensitive to BHs • Sensitive to core collapse history • ( à tests of star formation history) More BH (5 years) f BH ~ 0.2 ~ 0.05 ~ 0.03 Horiuchi et al (2018); Lunardini (2009), Lien et al Yuksel et al (2006) (2010), Yuksel & Kistler (2015), Moller et al (2018) Shunsaku Horiuchi (Virginia Tech) 22
MULTI-MESSENGER CONNECTIONS Shunsaku Horiuchi (Virginia Tech) 23
The next Galactic supernova LIGO VIRGO KAGRA ASAS-SN Palomar Subaru LSST + CR Super-K JUNO DUNE Hyper-Kamiokande Nakamura, Horiuchi et al (2016) Shunsaku Horiuchi (Virginia Tech) 24
Neutrino confidence Reveal IF: High number statistics expected from a Galactic core collapse Running Not shown: direct dark matter detectors Mirizzi et al (2015); Scholberg (2012) Shunsaku Horiuchi (Virginia Tech) 25
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