Three-dimensional Magnetohydrodynamical Simulations of a Core-Collapse Supernova

• Published in: The Astrophysical journal Vol. 683; no. 1; pp. 357 - 374
• Main Authors: Mikami, Hayato, Sato, Yuji, Matsumoto, Tomoaki, Hanawa, Tomoyuki
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 10.08.2008; University of Chicago Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Collapse; Three dimensional model; Supernovae; accretion, accretion disks; MHD; Numerical method; methods: numerical; Accretion disks; supemovae: general
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/589759

We show three-dimensional magnetohydrodynamical simulations of a core- collapse supernova in which the progenitor has magnetic fields inclined to the rotation axis. The simulations employed a simple empirical equation of state in which the pressure of degenerate gas is approximated by piecewise polytropes for simplicity. Energy loss due to neutrinos is not taken into account for simplicity as well. The simulations start from the stage of dynamical collapse of an iron core. The dynamical collapse halts at [image] ms by the pressure of high-density gas, and a proto-neutron star (PNS) forms. The evolution of the PNS was followed for about 40 ms in typical models. When the initial rotation is mildly fast and the initial magnetic fields are mildly strong, bipolar jets are launched from the upper atmosphere of the PNS. The jets are accelerated to [image] km s super(-1), which is comparable to the escape velocity at the footpoint. The jets are parallel to the initial rotation axis. Before the launch of the jets, magnetic fields are twisted by rotation of the PNS. The twisted magnetic fields form torus-shaped multilayers in which the azimuthal component changes alternately. The formation of magnetic multilayers is due to the initial condition in which the magnetic fields are inclined with respect to the rotation axis. The energy of the jet depends only weakly on the initial magnetic field assumed. When the initial magnetic fields are weaker, the time lag is longer between the PNS formation and jet ejection. It is also shown that the time lag is related to the Alfven transit time. Although the nearly spherical prompt shock propagates outward in our simulations, it is an artifact due to our simplified equation of state and neglect of neutrino loss. The morphology of twisted magnetic field and associate jet ejection are, however, not affected by the simplification.