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Supernova Neutrinos

Supernova Neutrinos. Christian Y. Cardall Oak Ridge National Laboratory Physics Division University of Tennessee, Knoxville Department of Physics and Astronomy. Core-collapse supernovae Survey of collapse simulations Supernova neutrino signals New effects at small ∆m 2 ?.

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Supernova Neutrinos

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  1. Supernova Neutrinos • Christian Y. Cardall • Oak Ridge National Laboratory • Physics Division • University of Tennessee, Knoxville • Department of Physics and Astronomy

  2. Core-collapse supernovae Survey of collapse simulationsSupernova neutrino signalsNew effects at small ∆m2?

  3. Core-collapse supernovae

  4. SN 1998aq (in NGC 3982)

  5. Type Ia (no H, strong Si) Type II (obvious H) Type I (no H) Type Ic (no H, He, Si) Type Ib (no H, obvious He) • Spectral classification of supernovae: Filippenko (1997)

  6. Rotation Magnetic Fields

  7. Some key ingredients are • Neutrino transport/interactions, • Spatial dimensionality; • Dependence on energy and angles; • Relativity; • Comprehensiveness of interactions; • (Magneto)Hydrodynamics/gravitation, • Dimensionality; • Relativity; • Equation of state/composition, • Dense matter treatments; • Number and evolution of nuclear species; • Diagnostics, • Accounting of lepton number; • Accounting of energy; • Accounting of momentum.

  8. The observables to understand include • Explosion (and energy thereof); • Neutrinos; • Remnant properties, • Mass, spin, kick velocity, magnetic fields; • Gravitational waves; • Element abundances; • Measurements across the EM spectrum, • IR, optical, UV, X-ray, gamma-ray;images, light curves, spectra, polarimetry...

  9. Survey of collapse simulations

  10. Neutrino radiation transport Magnetohydrodynamics

  11. Two observables beyond explosion… • Accretion continues until the stalled shock is reinvigorated: relation between neutron star mass and delay to explosion • The abundance of nuclei with a closed shell of 50 neutrons • The electron fraction…is set by neutrino interactions:

  12. Mezzacappa et al. (1998) Fryer & Warren (2002) • Fluid dynamics:2D • Neutrino transport: 1D + 1D • Fluid dynamics:2D, 3D • Neutrino transport: 2D + 0D, 3D + 0D

  13. Neutron star mass too small; heating drives explosion too soon. N=50 overproduction; Ye too low. Neutrino radiation transport Magnetohydrodynamics

  14. Liebendörfer et al. (2001, 2004) Rampp & Janka (2000, 2002) Thompson, Burrows, & Pinto (2002) Kitaura, Janka, & Hillebrandt (2006) • Fluid dynamics:1D • Neutrino transport: 1D + 2D

  15. Explosion only for 8-10 M stars with O-Ne-Mg cores. Reasonable neutron star mass; accretion continues during delay. Reasonable N=50 element production expected; ejected matter has Ye > 0.46. May explain some subluminous Type II-P. Neutrino radiation transport Magnetohydrodynamics

  16. Swesty & Myra (2005) Burrows et al. (2006) • Fluid dynamics:2D • Neutrino transport: 2D + 1D

  17. Explosion for 11, 15, 25 M progenitors. Some neutrino transport details left out; is the acoustic mechanism physical? Reasonable neutron star mass; accretion continues during delay. Not yet clear if Ye gives reasonable nucleosynthesis or if the model is resolved. Neutrino radiation transport Magnetohydrodynamics

  18. Buras et al. (2006) • Fluid dynamics:2D • Neutrino transport: 1.5D + 2D

  19. Full 180º allows an 11 M star to explode; what about higher mass progenitors? Reasonable neutron star mass; accretion continues during delay. Reasonable N=50 element production expected; some of ejecta has Ye > 0.5. Acoustic mechanism not yet probed. Neutrino radiation transport Magnetohydrodynamics

  20. Neutrino radiation transport Magnetohydrodynamics

  21. Supernova neutrino signals

  22. Neutrino predictions ca. 1987 • Did anyone do gravitational collapse as a Fermi problem? • Assume the stellar core is basically a white dwarf: a Chandrasekhar mass of 1.4 M and about 104 km. • Assume that the neutron star it collapses to is essentially a giant nucleus, and hence has density n = 0.16 fm-3. • From the mass and final density,

  23. Neutrino predictions ca. 1987 • How long will it take to collapse? The free-fall time scale is • The iron core is roughly half protons before collapse. Electron capture converts each proton to a neutron with the emission of an antineutrino. • Assume the neutrinos are trapped (check the consistency of this later). Then the number density of antineutrinos is half the final nucleon density.

  24. Neutrino predictions ca. 1987 • From the number density of antineutrinos, find their typical energy from the inter-particle spacing: • On what timescale will the neutrinos diffuse out? • This ‘validates’ the assumption of neutrino trapping.

  25. Neutrino predictions ca. 1987 • Almost forgot: the gravitational binding energy released during collapse will be released in neutrinos. • If neutrinos are trapped we expect all flavors to be produced. They will be emitted with a hierarchy of energies because differences in their interactions cause them to decouple at different radii:

  26. Neutrino predictions ca. 1987 • ~ 1s hydrodynamic simulations with decent neutrino transport (Wilson 1984)

  27. Burrows and Lattimer 1986 • Neutrino predictions ca. 1987 • ~ 20s ‘stellar evolution’ with crude transport

  28. SN 1987A Tarantula Nebula

  29. Raffelt (1999) Each “event” involves ~109 “messengers,”with at most 1 “detected” SN1987A sent ~1058 “messengers,”with ~two dozen detected • The lucky messengers…

  30. Burrows and Lattimer (1987) • Prediction vs. observation

  31. Liebendörfer et al. (2004) Buras et al. (2005) • A neutrino window into the supernova…

  32. Thompson et al. (2005) Sumiyoshi et al. (2006) Pons et al. (2001) • …could provide information about, for instance, rotation and the nuclear equation of state.

  33. Raffelt (2005) • Neutrino mixing unknowns: 13 and hierarchy

  34. New effects at small ∆m2?

  35. Duan et al. (2006)

  36. Duan et al. (2006)

  37. Core-collapse supernovae Survey of collapse simulationsSupernova neutrino signalsNew effects at small ∆m2?

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