Neutrino Transport Research Articles

Prompt convection in core collapse supernovae

We investigate prompt convection in core collapse supernovae and its consequences for the late-time shock evolution and supernova outcome. We examine the evolution of the core prior to the onset of convection and nd that the negative entropy gradients imprinted on the outer core by the weakening shock, which, along with the negative lepton gradient, drive the convection, are very sensitive to (1) the neutrino transport and microphysics included in the core collapse simulation and (2) the nuclear equation of state. We perform a number of detailed one-dimensional spherically symmetric simulations of prompt convection using a mixing length algorithm in a code coupling the core hydrodynamics with multigroup uxlimited di usion of neutrinos of all types. We nd that prompt convection does not have a signi cant e ect on the neutrino luminosities or spectra in the postshock region and, consequently, on the late-time postshock neutrino heating and shock evolution. Consequently, we do not nd that prompt convection is important for the supernova explosion mechanism. 2

Maximum entropy distribution and closure for Bose-Einstein and Fermi-Dirac radiation transport

view Abstract Citations (46) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Maximum Entropy Distribution and Closure for Bose-Einstein and Fermi-Dirac Radiation Transport Cernohorsky, J. ; Bludman, S. A. Abstract We derive and study the variable Eddington factors following without approximation from the maximum entropy distribution. A unified formalism is developed for classical Maxwell-Boltzmann, Bose-Einstein, and Fermi-Dirac radiation. In the classical and high occupancy limits the maximum entropy closure is bounded by previously known variable Eddington factors that depend only on the flux: the Levermore-Pomraning closure for Bose radiation at high occupation density and Minerbo's flux-limiter for the Boltzmann limit of either quantum statistics. For immediate occupancy, the maximum entropy closure depends on both the occupation density and the flux. The Fermi-Dirac maximum entropy variable Eddington factor exhibits scale invariance, which leads to a simple analytic closure for fermion radiation. This Fermi-Dirac variable Eddington factor agrees well with Monte Carlo neutrino transport closures during early stages of neutron star formation. Publication: The Astrophysical Journal Pub Date: September 1994 DOI: 10.1086/174640 Bibcode: 1994ApJ...433..250C Keywords: Eddington Approximation; Fermi-Dirac Statistics; Maximum Entropy Method; Neutron Stars; Quantum Statistics; Radiation Transport; Star Formation; Stellar Radiation; Closure Law; Formalism; Maxwell-Boltzmann Density Function; Neutrinos; Transport Properties; Astrophysics; RADIATION MECHANISMS: NONTHERMAL; STARS: NEUTRON full text sources ADS |

3+1 general relativity by computer

We present some programs constructed to write the Einstein and matter conservation equations under the ADM or 3+1 formalism of general relativity as well as the relativistic Boltzmann equation in a fully covariant treatment. The programs are well suited to work in any coordinate system, but as a concrete application we treat the case of axisymmetric relativistic rotating systems and neutrino transport in spherical collapse.

A Convective Trigger for Supernova Explosions

The shock wave that stalls within ∼10 ms of its creation during the collapse and bounce of the core of a massive star leaves behind it unstable lepton and entropy profiles that can drive a violent Rayleigh-Taylor-like overturn. Coupling two-dimensional hydrodynamics with independent one-dimensional neutrino transport in 100 angular bins, we demonstrate the possible existence of a convective boost in the neutrino luminosities that can ignite a supernova explosion. While the shock-imposed negative entropy gradient drives the early convection, neutrino heat transfer can smooth it within 15 ms. However, the negative lepton gradient, generically created at shock break-out, is not smoothed and is reponsible for vigorous mantle overturn just interior to the early entropy spike

Stellar core collapse - A Boltzmann treatment of neutrino-electron scattering

Neutrino-electron scattering plays a major role in the deleptonization of the iron core during the gravitational collapse of a presupernova star and, hence, plays a major role in the success or failure of the shock ejection mechanism for Type II supernovae. In this paper we present the first simulation of realistic gravitational collapse in which neutrino-electron scattering is not aproximated in the neutrino transport equation with either a truncated Legendre series or a Fokker-Planck approximation. We begin with a 1.17 M ○. iron core extracted from a Nomoto-Hashimoto 13 Ma presupernova star

Type II supernovae and Boltzmann neutrino transport - The infall phase

We present the results from a computer simulation of the gravitational collapse of a 1.17 M ○ . iron core extracted from a Nomoto-Hashimoto 13 M ○ . presupernova star. The results are obtained with a Newtonian gravity, O(v/c) Lagrangian hydrodynamics code coupled to an O(v/c) Boltzmann solver for the neutrino transport. We include electron capture on nuclei and free protons and electron neutrino absorption on nuclei and free neutrons. We also include conservative scattering of electron neutrinos on free protons and neutrons and conservative coherent scattering of electron-neutrinos on nuclei. We use the Baron-Cooperstein equation of state

Flux-limited diffusion in hydrodynamics

The radiation transport equation, correct to order v/c, is used to derive a flux limiter valid in high-velocity hydrodynamic flows. In the limit v = 0 the widely used result of Levermore and Pomraning (LP) (1982) is recovered. In the case of homologous flow (v varies as R) the LP result remains valid, but in the presence of shock waves and other nonhomologous flows differences may be large. We calculate the Eddington factors, which are significantly altered, and discuss the importance of having them possess the correct form in the presence of a shock wave, e.g., on the neutrino transport during the formation of a supernova.

Relativistic two-moment neutrino transport

view Abstract Citations (13) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Relativistic Two-Moment Neutrino Transport Cernohorsky, J. ; van Weert, Ch. G. Abstract We implement a general relativistic neutrino transport scheme appropriate to problems in stellar collapse and neutron star formation. In this scheme the spectral energy and momentum balance equations are solved as a coupled set. We perform transport calculations on two frozen stellar background models neglecting the feedback of the neutrinos on the matter. We compare with schemes that ignore either relativity or momentum balance or both. The work performed by the neutrino stress on the matter is taken into account and has an important effect. In particular, if there is a hydrodynamical shock in the system, this work contribution boosts the energy deposition behind the shock. This may enhance the chances for a successful neutrino driven supernova explosion. Publication: The Astrophysical Journal Pub Date: October 1992 DOI: 10.1086/171848 Bibcode: 1992ApJ...398..190C Keywords: Gravitational Collapse; Neutrinos; Neutron Stars; Relativistic Particles; Star Formation; Transport Theory; Computational Astrophysics; Shock Waves; Spectral Energy Distribution; Stellar Composition; Stellar Interiors; Stellar Models; Astrophysics; ELEMENTARY PARTICLES; RELATIVITY; SHOCK WAVES; STARS: INTERIORS full text sources ADS |

Neutrino radiation from supernovae

In a supernova event about 10 53 erg of gravitational binding energy are released, the bulk of which is carried off by neutrinos. The neutrino burst detected in February 1987 recorded a supernova explosion that took place in the Large Magellanic Cloud some 50 kpc away from the earth and confirmed the basics of models of stellar collapse. Indeed, the neutrino luminosity inferred from observation agrees with the luminosity predicted by detailed model calculations of neutrino transport. However, there is some room (within the uncertainties of both theory and observation) for extra exotic sources of energy drain. Among them, there are right-handed neutrinos, which appear in almost any extension of the minimal standard model of electroweak interactions. In particular, if neutrinos are massive Dirac particles, the right-handed degrees of freedom should be copiously emitted in a supernova collapse. Using SN1987A data one can place bounds on neutrino masses or on the magnetic moment of the neutrino. Furthermore, independently of the energetics of stellar dynamics, the actual detection of neutrinos at IMB and Kamioka has led to relevant limits on neutrino mass, neutrino lifetime, and neutrino charge.

Neutrino neutral current interactions in nuclear matter

Detailed knowledge of neutrino transport properties in matter is crucial for an understanding of the evolution of supernovae and of neutron star cooling. We investigate screening of neutrino scattering from a dense degenerate gas of electrons, protons and neutrons. We take into account correlations induced by the Coulomb interactions of the electrons of the electrons and protons, and the strong interactions of the protons and neutrons. Nuclear matter is described by the σω model of quantum hadrodynamics. Results are presented for typical astrophysical scenarios. The differential cross section is strongly reduced at large energy transfer, where electrons dominate, and slightly reduced for small energy transfer, where nucleons dominate. At large densities, the nucleon effective mass is considerably lower than the free mass, and the region dominated by nucleons extends to larger energy transfer than for free nucleons.

Exact expressions and improved approximations for interaction rates of neutrinos with free nucleons in a high-temperature, high-density gas

view Abstract Citations (24) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Exact Expressions and Improved Approximations for Interaction Rates of Neutrinos with Free Nucleons in a High-Temperature, High-Density Gas Schinder, Paul J. Abstract The exact expressions needed in the neutrino transport equations for scattering of all three flavors of neutrinos and antineutrinos off free protons and neutrons, and for electron neutrino absorption on neutrons and electron antineutrino absorption on protons, are derived under the assumption that nucleons are noninteracting particles. The standard approximations even with corrections for degeneracy, are found to be poor fits to the exact results. Improved approximations are constructed which are adequate for nondegenerate nucleons for neutrino energies from 1 to 160 MeV and temperatures from 1 to 50 MeV. Publication: The Astrophysical Journal Supplement Series Pub Date: September 1990 DOI: 10.1086/191498 Bibcode: 1990ApJS...74..249S Keywords: Interstellar Gas; Neutrinos; Neutron Stars; Stellar Interiors; Absorption Spectra; Antineutrinos; Electron Scattering; Emission Spectra; Particle Interactions; Supernovae; Astrophysics; DENSE MATTER; ELEMENTARY PARTICLES; NEUTRINOS; STARS: INTERIORS; STARS: SUPERNOVAE full text sources ADS |

Maximum entropy eddington factors in flux-limited neutrino diffusion

A neutrino transport scheme for use in dense stellar environments and collapsing stars is constructed. The maximum entropy principle is used to establish the general form of the angular neutrino distribution function. The two Lagrange multipliers introduced by this procedure are determined by using the flux-limited diffusion theory (FDT) of Levermore and Pomraning. In contrast to standard practice in radiation (photon) transport, the anisotropic scattering contribution is taken into account. Its inclusion leads to a modification of the Levermore-Pomraning approach. The transition from a multigroup to an energy-integrated transport scheme for FDT is investigated. In particular, the link to the two-fluid model of Cooperstein et al is made.

Neutrino transport during the core bounce phase of a type II supernova explosion

A Monte Carlo study of neutrino transport in the vicinity of the outward-moving core bounce shock of a Type II SN is discussed. The method takes into account energy gains and losses produced by first-order Fermi shock acceleration and inelastic collisions with nuclei and electrons. Sources of neutrino opacity considered include scattering off electrons, nucleons, and nuclei, the absorption of electron neutrinos, and neutrino pair annihilation. Previous SN models have been used to determine the time-integrated energy spectra of the three neutrino flavors in order to determine the conditions in the star's collapsing core. 63 refs.

The prompt-shock supernova mechanism. II - Supranuclear EOS behavior and the precollapse model

The author's study of the prompt shock mechanism continues with an investigation of the effect of the softness of the supranuclear behavior of the equation of state (EOS), and of the structure of the precollapse core model. Three different levels of neutrino transport were incorporated in the calculations. When neutrino-electron scattering (NES) is turned off and only e-type neutrinos are transported, vigorous explosions are produced for a wide range of supranuclear EOS parameters and initial models. The inclusion of NES requires soft supranuclear behavior and low mass and entropy precollapse models for successful explosions. The inclusion of all neutrino flavors further reduces the available parameter space and restricts the precollapse core configurations for successful explosions. It is found that the current generation of precollapse models do not produce prompt-shock explosions when the most realistic/optimistic physics is used. The requisite modifications of the precollapse models for successful prompt-shock explosions are discussed. 30 refs.

Neutrino transport and the prompt mechanism for type II supernovae

view Abstract Citations (59) References (67) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Neutrino Transport and the Prompt Mechanism for Type II Supernovae Myra, Eric S. ; Bludman, Sidney A. Abstract Consideration is given to the possibility that a soft nuclear equation of state and general relativistic hydrodynamics can produce a shock with sufficient strength to propagate directly through a low-mass iron core during a stellar collapse. It is found that neutrino-electron scattering produces shock failure due to neutrino downscatter during collapse. Neutrino-electron scattering has little effect during shock propagation. It is shown that neutrino-matter energy exchange is important at densities below trapping density. Publication: The Astrophysical Journal Pub Date: May 1989 DOI: 10.1086/167401 Bibcode: 1989ApJ...340..384M Keywords: Neutrinos; Stellar Interiors; Supernovae; Electron Capture; Electron Scattering; Equations Of State; Heavy Nuclei; Relativity; Shock Wave Propagation; Supernova 1987a; Astrophysics; DENSE MATTER; EQUATION OF STATE; NEUTRINOS; SHOCK WAVES; STARS: INTERIORS; STARS: SUPERNOVAE full text sources ADS | data products SIMBAD (1)

The prompt-shock supernova mechanism. I - The effect of the free-proton mass fraction and the neutrino transport algorithm

view Abstract Citations (91) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Prompt-Shock Supernova Mechanism. I. The Effect of the Free-Proton Mass Fraction and the Neutrino Transport Algorithm Bruenn, Stephen W. Abstract Results are presented of an extensive numerical investigation of the prompt-shock supernova mechanism. This paper focuses on the effect of the free-proton mass fraction Xp given by the equation of state (EOS) and of the various levels of standard neutrino physics on the success of the bounce shock in producing a supernova-like explosion in a prompt manner. When neutrino-electron scattering (NES) is turned off and only e-type neutrinos are transported, vigorous explosions are produced for a wide range of values for Xp. The inclusion of NES considerably restricts the possible values of Xp for successful explosions. The additional inclusion of all neutrino flavors further restricts the possible values of Xp. Successful shocks can still be produced (depending on how the shock energy is defined), but only for very small values of Xp. Publication: The Astrophysical Journal Pub Date: May 1989 DOI: 10.1086/167450 Bibcode: 1989ApJ...340..955B Keywords: Neutrinos; Nuclear Astrophysics; Shock Wave Propagation; Supernovae; Astronomical Models; Electron Scattering; Equations Of State; Transport Theory; Astrophysics; NEUTRINOS; SHOCK WAVES; STARS: INDIVIDUAL ALPHANUMERIC: SN 1987A; STARS: INTERIORS; STARS: SUPERNOVAE full text sources ADS | data products SIMBAD (1) Related Materials (1) Part 2: 1989ApJ...341..385B

General relativistic neutrino transport in stellar collapse

view Abstract Citations (36) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS General Relativistic Neutrino Transport in Stellar Collapse Baron, E. ; Myra, E. S. ; Cooperstein, J. ; van den Horn, L. J. Abstract The radiative hydrodynamic equations for a coupled system of neutrino radiation and matter within a fully general relativistic framework are derived. The system is assumed to be spherically symmetric, and the neutrino component amenable to solution via angular moment methods. The neutrinos are not assumed to be in equilibrium with the matter. The form of these equations is especially applicable to the numerical solution of problems in stellar collapse and neutron star formation. In such problems, general relativistic effects are of possibly critical importance but do not dominate to the extent that use of a diagonal form of the metric causes problems. Publication: The Astrophysical Journal Pub Date: April 1989 DOI: 10.1086/167352 Bibcode: 1989ApJ...339..978B Keywords: Gravitational Collapse; Neutrinos; Relativistic Effects; Stellar Physics; Transport Theory; Angular Momentum; Hydrodynamics; Neutron Stars; Red Shift; Space-Time Functions; Astrophysics; HYDRODYNAMICS; NEUTRINOS; RELATIVITY; STARS: COLLAPSED full text sources ADS | data products SIMBAD (1)

Diagonal and off-diagonal density fluctuations in hot nuclear matter, and applications to neutrino transport in supernovae.

We calculate the effects of interactions on the density fluctuations of an $n$, $p$, $e$ plasma. The scattering of neutrinos arising from the Fermi part of the neutral current interactions with protons, under supernova conditions, is practically extinguished by Coulomb effects in the plasma. Charged-current reactions are discussed in terms of off-diagonal density fluctuations. Inclusion of the symmetry energy term in the nuclear interaction gives rise to a large reduction in the Fermi part of the cross section for $\ensuremath{\nu}+n\ensuremath{\rightarrow}{e}^{\ensuremath{-}}+p$.

Gravitational radiation from type-II supernovae: The effect of the high-density equation of state.

Odd-parity gravitational perturbations of detailed spherically symmetric type-II supernova models, which include realistic equations of state and neutrino transport, are studied in the linearized Einstein theory. To investigate the parameters affecting gravitational-wave production during core collapse, we have performed simulations in which we vary the equation of state at supernuclear densities, the free proton mass fraction, and the precollapse iron core. These variations span much of the range of conditions currently thought to occur during stellar collapse and lead to the production of core-bounce shock waves that vary from the very strong to those that stall almost immediately. We find little difference in the gravitational radiation output among any of these models, though models that use stiffer equations of state or higher-mass iron cores give somewhat more radiation output.

General-relativistic radiation hydrodynamics and neutrino transport in polar-sliced space-time.

Extending the work of Schinder, Bludman, and Piran, I derive the equations of radiation hydrodynamics in polar-sliced space-time. The additional terms which describe the effects of neutrino stress energy on the gas dynamics are added to the equations of hydrodynamics. The neutrino Boltzmann equation and its lowest angular and energy moments are derived in comoving coordinates with neutrino energies and directions determined in comoving frames. It is shown that the Boltzmann equation gives the correct results when neutrinos are strongly trapped, and the neutrinos become just another component of a perfect gas. Techniques which I plan to use to numerically solve the neutrino transport equations are discussed.