Protoneutron Star Winds:

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Neutrino Production in Supernovae
Todd ThompsonPrinceton University
With S. Reddy, J. Horvath, A. Burrows
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Outline

• Introduction The Supernova Problem
• One Ingredient Neutrino Microphysics
• Models of Core-Collapse Supernovae
• Is it possible to significantly modify the
  neutrino signature?
• The Energy Budget, Relic Neutrinos, Detection
• Summary, Conclusions, The Future

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The Energy Budget

• Gravity

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Observing Proto-Neutron Stars

• Direct signatures of collapse
• Neutrino signal
• Gravitational wave signal
• Indirect diagnostics
• Supernova remnant (energy, morphology, 56Ni
  yield)
• Nucleosynthesis (r-process, neutrino processing)
• NS spin distribution ( P1?, 10, 100, 1000 ms)
• NS magnetic field strengths (B 1012, 1015 G)
• NS velocities (0 km s-1 lt V lt 1500 km s-1)

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Neutron Star Birth in Real Time The Neutrino
Signature
SN 1987A LMC D50 kpc 18-19 Neutrino events in
15 seconds.
from Burrows (1988)
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Neutron Star Birth in Real Time The Neutrino
Signature
SN 2006(??) D10 kpc SuperKamiokande observes
600 - 1000 neutrino events in 0.25 seconds.
Thompson et al. (2003)
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• What is a Core-Collapse Supernova?
• An explosion initiated by a dynamical instability
• The death of a massive star
• The birth cry of a neutron star or black hole
• An agent of chemical and dynamical galactic
  evolution
• Characteristics of Supernovae
• Total kinetic energy 1051 ergs
• Luminous energy radiated 1049 ergs
• Temperatures 0.1 20 MeV (10 MeV1011 K)
• Densities 1010 6 x 1014 g cm-3
• Neutrino Production
• Neutrino energy radiated 2-3 x 1053 ergs
• Core is opaque to neutrinos of all flavors!

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The Progenitor
Shock Revival Explosion 0.5 s
Prompt Shock Stalls ( ms) R100 km
Instability Collapse
Bounce
Bounce Shock Formation
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The Progenitor
Post-explosion neutron star cooling epoch
Cooling Epoch
Newly-born neutron star cools, contracts.
Instability Collapse
E?1053 ergs
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Mass Flux
250 km
100 km
60 km
from Janka Mueller (1996)
Net Heating
Dense Core
Neutrinosphere
Gain Radius
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Neutrino Processes

• Charged-current interactions dominate heating and
  cooling
• Pair-production
• Scattering opacities

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The Boltzmann Equation
The Collision Term
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Neutrino Production Rate (s-1)
T
?
Neutrino Energy (MeV)
r
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e.g., Inelastic Neutrino-Electron Scattering
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Dynamical Models of Supernovae

• Ingredients
• Hydrodynamics Newtonian, explicit, Lagrangian
• High-density EOS Lattimer-Swesty, liquid drop
  model
• (Lattimer Swesty 1991) --- BUT, see Shen et al.
  (1998)
• Neutrino Transport Feautrier technique,
  tangent-ray, ALI
• Neutrino Microphysics Opacities,
  emission/absorption, new inelastic scattering
  algorithm
• Thompson et al. (2003)
• Rampp Janka (2000) Liebendorfer (2000)
  Sumiyoshi et al. (2005) Precision transport
  Yamada (1997) Yamada et al. (1999)

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Free Protons
Nuclei
Mass Flux
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Higher energy implies higher opacity.
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Emergent Neutrino Spectra, Heirarchy
? ? neutrinos decouple at higher density and
temperature than e-type neutrinos.
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Time Dependence of Neutrino Spectra
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What Modifies the Neutrino Signature?

• Changes to microphysics in the core.

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Possible Modifications to Standard Neutrino
Production

• Many-body effects at high density. Reddy et al.
  (1998) Raffelt Seckel (1998) Burrows Sawyer
  (1998) Yamada Toki (2000)
• Many-body effects at low density. Horowitz et
  al. (2004), (2005)
• Very high large-scale magetic fields. Qian
  Lai (1998) Arras Lai (1999) Kotake et al.
  (2004)
• Non-thermal effects Coronae? Ramirez-Ruiz
  Socrates (2005)
• Others?

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What Modifies the Neutrino Signature?

• Microphysics?
• Neutrinos production/absorption, opacity.
• Macrophysics?
• Progenitor structure, rotation rate.
• Also, multi-dimensional effects, shadowing, etc.

Walder et al. (2005) Kotake et al. (2003)
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Progenitor Dependence
Accretion luminosity dominates, set by density
profile.
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Rotation Supernovae

• Rapid rotation modifies the neutrino signature by
  modifying the thermal structure of the core.
• It also introduces another timescale.
• Rotating collapse generates shear (d?/dr).
• The free energy of differential rotation (shear
  energy) can be tapped by viscous processes on a
  viscous timescale.
• Rapid rotation viscous heating modifies dynamics
  significantly ? Explosions.
• Viscosity maybe magnetic torques

T. Thompson, Quataert, Burrows 2005
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Justification for Rapid Rotation

• Magnetars (10 of supernovae).
• Asymmetries in supernova ejecta,
  spectropolarimetry. (L. Wang, C. Wheeler)
• Massive stars rotate rapidly
• Recent models (Heger Woosley).
• Connection between supernovae and GRBs.
• Accretion induced collapse of white dwarfs.
• But, neutron stars thought to be born slowly
  rotating.

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Oblate Neutrino-spheres inRapidly Rotating
Core-Collapse
Dessart et al. (2006)
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Rapidly Rotating Core-Collapse
Dessart et al. (2006)
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The Surface Temperature inRapidly Rotating
Core-Collapse
Dessart et al. (2006)
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The Energy Budget

• Fundamentally inescapably
• Luminosity is dictated by diffusion.
• For very rapid rotation (P1 ms), some binding
  energy is trapped as shear dissipated on a
  viscous time.
• Reasonable modifications just order unity.

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Some Numbers

• For a supernova at D 10 kpc, 10,000 ? events
  detected by SK (30kt) in 10 seconds.
• (108 people experience a charged-current
  interaction!)
• 1019 stars ? 1017 SNe, 1053 ergs SN-1 ? E?1070
  ergs (Eph) ???? 10 MeV ? 1074.8 ?s.
• Star formation at z1 ? Gpc scales ? ? number
  flux of 1 cm-2 s-1 MeV-1 ? 1 event yr-1 in SK.
• But, ?s with ???? 10 MeV/(1z) are unobservable
  because of backgrounds ? estimate decreases.

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Neutron Star Birth in Real Time The Neutrino
Signature
SN 1987A LMC D50 kpc 18-19 Neutrino events in
15 seconds.
from Burrows (1988)
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Relic Neutrinos

• Star formation rate density.
• IMF (massive stars).
• IMF (black holes).
• Convolve with detector and backgrounds.
• Lastly, neutrino oscillations during exit of the
  massive stellar progenitor affect relic
  population.

Mihos, Illingworth
Totani, Sato, Yoshii 1995 Totani Sato
1996 Ando Sato 2003, 2004 Takahashi et al.
2001, 2003
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Summary

• Neutrinos are important because they probe the
  core at formation (even if not integral to the
  explosion mechanism).
• A 300 kt detector (10?SK) sees 1 ? from a SN at
  3 Mpc. A 300 Mt detector sees 1
  ? from a SN at 100 Mpc.
• M82, a starburst at 3 Mpc, has a SN rate of
  0.02 yr-1.
• Arp 220, a ULIRG at 76 Mpc, has a supernova rate
  of 2 yr-1.
• 1987A strongly constrains the MeV neutrino
  emission during neutron star formation.
• Neutrino production and transport are
  well-understood.
• L? on second timescales may be modified at the
  factor of 2 level by the progenitor structure
  and/or rotation.
• The binding energy of neutron stars, coupled with
  the SF history of the universe, dictates the
  relic neutrino background.

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The End