Three-dimensional simulations of stellar core collapse in full general relativity: Nonaxisymmetric dynamical instabilities
- Graduate School of Arts and Sciences, University of Tokyo, Tokyo, 153-8902 (Japan)
We perform fully general relativistic simulations of rotating stellar core collapse in three spatial dimensions. The hydrodynamic equations are solved using a high-resolution shock-capturing scheme. A parametric equation of state is adopted to model collapsing stellar cores and neutron stars following Dimmelmeier et al. The early stage of the collapse is followed by an axisymmetric code. When the stellar core becomes compact enough, we start a three-dimensional simulation adding a bar-mode nonaxisymmetric density perturbation. The axisymmetric simulations are performed for a wide variety of initial conditions changing the rotational velocity profile, parameters of the equations of state, and the total mass. It is clarified that the maximum density, the maximum value of the compactness, and the maximum value of the ratio of the kinetic energy T to the gravitational potential energy W ({beta}{identical_to}T/W) achieved during the stellar collapse and bounce depend sensitively on the velocity profile and the total mass of the initial core and equations of state. It is also found that for all the models with a high degree of differential rotation, a funnel structure is formed around the rotational axis after the formation of neutron stars. For selected models in which the maximum value of {beta} is larger than {approx}0.27, three-dimensional numerical simulations are performed. It is found that the bar-mode dynamical instability sets in for the case that the following conditions are satisfied: (i) the progenitor of the stellar core collapse should be rapidly rotating with the initial value of 0.01 < or approx. {beta} < or approx. 0.02 (ii) the degree of differential rotation for the velocity profile of the initial condition should be sufficiently high, and (iii) a depletion factor of pressure in an early stage of collapse should be large enough to induce a significant contraction to form a compact stellar core for which an efficient spin-up can be achieved surmounting the strong centrifugal force. As a result of the onset of the bar-mode dynamical instabilities, the amplitude of gravitational waves can be by a factor of {approx}10 larger than that in the axisymmetric collapse. It is found that a dynamical instability with the m=1 mode is also induced for the dynamically unstable cases against the bar mode, but the perturbation does not grow significantly and, hence, it does not contribute to an outstanding amplification of gravitational waves. No evidence for fragmentation of the protoneutron stars is found in the first few 10 msec after the bounce.
- OSTI ID:
- 20705832
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 71, Issue 2; Other Information: DOI: 10.1103/PhysRevD.71.024014; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AMPLITUDES
AXIAL SYMMETRY
COMPUTERIZED SIMULATION
COSMOLOGY
DISTURBANCES
EQUATIONS OF STATE
GENERAL RELATIVITY THEORY
GRAVITATIONAL WAVES
INSTABILITY
KINETIC ENERGY
NEUTRON STARS
POTENTIAL ENERGY
RELATIVISTIC RANGE
ROTATION
SPIN
THREE-DIMENSIONAL CALCULATIONS