Neutrino crown of a protoneutron star and analysis of its convective instability

Journal Article · Sat Apr 15 00:00:00 EDT 2006 · Physics of Atomic Nuclei

DOI:https://doi.org/10.1134/S1063778806040090· OSTI ID:21076083

Litvinova, I Yu ^[1]

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1. Institute of Theoretical and Experimental Physics (Russian Federation)

A numerical solution to the problem of the structure of the neutrino crown of a protoneutron star that is formed upon an iron-star-core collapse, which is peculiar to all massive stars at the end of their thermonuclear evolution, is given. The structure of a neutrino crown, which is semitransparent to neutrino radiation from a spherical layer between the neutrino sphere and the front of the accretion shock wave, is determined by a set of nonlinear ordinary differential equations of spherically symmetric neutrino hydrodynamics with allowance for a complete set of beta processes in a Boltzmann free-nucleon gas and an ultrarelativistic Fermi-Dirac electron-positron gas that form neutrino-crown matter. The problem of consistently taking into account nonequilibrium neutrino-absorption and neutrino-emission processes and the problem of formulating boundary conditions for a neutrino crown were the main problems in constructing the numerical solution in question, which was obtained by means of a dedicated algorithm. The problem at hand features a number of parameters: the protoneutron-star mass, M{sub 0}; the rate of accretion of the outer layers of the collapsing star being considered, oM{sub 0}; the effective temperature of the neutrino sphere and the effective neutrino chemical potential there, T{sub veff} and {psi}{sub veff}, respectively; and, finally, the total neutrino emissivity of the neutrino sphere, L{sub {nu}}{sub {nu}}{sub -tilde}. Two of these parameters, M{sub 0} and L{sub {nu}}{sub {nu}}{sub -tilde}, are varied within broad intervals in accordance with the hydrodynamic theory of a collapse. On one hand, the numerical solutions constructed in the present study give an idea of the physical conditions in the immediate vicinity of a protoneutron star in the course of its continuing gravitational collapse; on the other hand, they make it possible to obtain exhaustive information about its convective instability, which is the most important property of a so-called soundless collapse-that is, a collapse not accompanied by an explosion of a supernova scale. The increment of the development of a convective instability is obtained at a linear stage, this giving sufficient grounds to introduce the hypothesis that the instability in question plays a key role in the origin of observed gamma-ray bursts. More precisely, these bursts may result from the development of the instability at the subsequent nonlinear stage, which has yet to be studied theoretically-in particular, on the basis of non-one-dimensional numerical models of neutrino hydrodynamics.

• OSTI ID: 21076083
• Journal Information: Physics of Atomic Nuclei, Vol. 69, Issue 4; Other Information: DOI: 10.1134/S1063778806040090; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7788
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ABSORPTION
ALGORITHMS
BOUNDARY CONDITIONS
CONVECTIVE INSTABILITIES
COSMIC GAMMA BURSTS
DIFFERENTIAL EQUATIONS
ELECTRIC GROUNDS
ELECTRONS
EMISSION
EMISSIVITY
EVOLUTION
EXPLOSIONS
GRAVITATIONAL COLLAPSE
HYDRODYNAMICS
HYPOTHESIS
IRON
LAYERS
MASS
NEUTRINOS
NONLINEAR PROBLEMS
NUCLEONS
NUMERICAL SOLUTION
ONE-DIMENSIONAL CALCULATIONS
POSITRONS
RELATIVISTIC RANGE
SHOCK WAVES
SPHERICAL CONFIGURATION
STARS
SUPERNOVAE