General relativistic magnetohydrodynamic simulations of collapsars

Yosuke Mizuno, Shoichi Yamada, Shinji Koide, Kazunari Shibata

    Research output: Contribution to journalArticle

    58 Citations (Scopus)

    Abstract

    We have performed 2.5-dimensional general relativistic magnetohydrodynamic (MHD) simulations of the gravitational collapse of a magnetized rotating massive star as a model of gamma-ray bursts (GRBs). The current calculation focuses on general relativistic MHD with simplified microphysics (we ignore neutrino cooling, physical equation of state, and photodisintegration). Initially, we assume that the core collapse has failed in this star. A few M black hole is inserted by hand into the calculation. The simulations presented in the paper follow the accretion of gas into a black hole that is assumed to have formed before the calculation begins. The simulation results show the formation of a disklike structure and the generation of a jetlike outflow inside the shock wave launched at the core bounce. We have found that the jet is accelerated by the magnetic pressure and the centrifugal force and is collimated by the pinching force of the toroidal magnetic field amplified by the rotation and the effect of geometry of the poloidal magnetic field. The maximum velocity of the jet is mildly relativistic (∼0.3c). The velocity of the jet becomes larger as the initial rotational velocity of stellar matter gets faster. On the other hand, the dependence on the initial magnetic field strength is a bit more complicated: the velocity of the jet increases with the initial field strength in the weak field regime, then is saturated at some intermediate field strength, and decreases beyond the critical field strength. These results are related to the stored magnetic energy determined by the balance between the propagation time of the Alfvén wave and the rotation time of the disk (or twisting time).

    Original languageEnglish
    Pages (from-to)395-412
    Number of pages18
    JournalAstrophysical Journal
    Volume606
    Issue number1 I
    DOIs
    Publication statusPublished - 2004 May 1

    Fingerprint

    magnetohydrodynamic simulation
    magnetohydrodynamics
    field strength
    magnetic field
    simulation
    magnetic fields
    centrifugal force
    gravitational collapse
    twisting
    shock wave
    massive stars
    gamma ray bursts
    equation of state
    shock waves
    equations of state
    outflow
    neutrinos
    accretion
    cooling
    geometry

    Keywords

    • Accretion, accretion disks
    • Black hole physics
    • Gamma rays: bursts
    • Methods: numerical
    • MHD
    • Supernovae: general

    ASJC Scopus subject areas

    • Space and Planetary Science

    Cite this

    General relativistic magnetohydrodynamic simulations of collapsars. / Mizuno, Yosuke; Yamada, Shoichi; Koide, Shinji; Shibata, Kazunari.

    In: Astrophysical Journal, Vol. 606, No. 1 I, 01.05.2004, p. 395-412.

    Research output: Contribution to journalArticle

    Mizuno, Yosuke ; Yamada, Shoichi ; Koide, Shinji ; Shibata, Kazunari. / General relativistic magnetohydrodynamic simulations of collapsars. In: Astrophysical Journal. 2004 ; Vol. 606, No. 1 I. pp. 395-412.
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    abstract = "We have performed 2.5-dimensional general relativistic magnetohydrodynamic (MHD) simulations of the gravitational collapse of a magnetized rotating massive star as a model of gamma-ray bursts (GRBs). The current calculation focuses on general relativistic MHD with simplified microphysics (we ignore neutrino cooling, physical equation of state, and photodisintegration). Initially, we assume that the core collapse has failed in this star. A few M⊙ black hole is inserted by hand into the calculation. The simulations presented in the paper follow the accretion of gas into a black hole that is assumed to have formed before the calculation begins. The simulation results show the formation of a disklike structure and the generation of a jetlike outflow inside the shock wave launched at the core bounce. We have found that the jet is accelerated by the magnetic pressure and the centrifugal force and is collimated by the pinching force of the toroidal magnetic field amplified by the rotation and the effect of geometry of the poloidal magnetic field. The maximum velocity of the jet is mildly relativistic (∼0.3c). The velocity of the jet becomes larger as the initial rotational velocity of stellar matter gets faster. On the other hand, the dependence on the initial magnetic field strength is a bit more complicated: the velocity of the jet increases with the initial field strength in the weak field regime, then is saturated at some intermediate field strength, and decreases beyond the critical field strength. These results are related to the stored magnetic energy determined by the balance between the propagation time of the Alfv{\'e}n wave and the rotation time of the disk (or twisting time).",
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