Magnetically dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions

Dmitri A. Uzdensky, Andrew I. MacFadyen

    Research output: Contribution to journalArticle

    Abstract

    It has been suggested that magnetic fields play a dynamically important role in core-collapse explosions of massive stars. In particular, they may be important in the collapsar scenario for gamma-ray bursts (GRB), where the central engine is a hyperaccreting black hole or a millisecond magnetar. The present paper is focused on the magnetar scenario, with a specific emphasis on the interaction of the magnetar magnetosphere with the infalling stellar envelope. First, the "pulsar-in-a-cavity" problem is introduced as a paradigm for a magnetar inside a collapsing star. The basic setup of this fundamental plasma-physics problem is described, outlining its main features, and simple estimates are derived for the evolution of the magnetic field. In the context of a collapsing star, it is proposed that, at first, the ram pressure of the infalling plasma acts to confine the magnetosphere, enabling a gradual buildup of the magnetic pressure. At some point, the growing magnetic pressure overtakes the (decreasing) ram pressure of the gas, resulting in a magnetically driven explosion. The explosion should be highly anisotropic, as the hoop stress of the toroidal field, confined by the surrounding stellar matter, collimates the magnetically dominated outflow into two beamed magnetic-tower jets. This creates a clean narrow channel for the escape of energy from the central engine through the star, as required for GRBs. In addition, the delayed onset of the collimated-explosion phase can explain the production of large quantities of nickel-56, as suggested by the GRB-supernova connection. Finally, the prospects for numerical simulations of this scenario are discussed.

    Original languageEnglish (US)
    Article number056506
    JournalPhysics of Plasmas
    Volume14
    Issue number5
    DOIs
    StatePublished - 2007

    Fingerprint

    magnetars
    gamma ray bursts
    supernovae
    explosions
    stars
    ram
    magnetospheres
    engines
    stellar envelopes
    hoops
    plasma physics
    towers
    massive stars
    magnetic fields
    pulsars
    escape
    nickel
    cavities
    estimates
    gases

    ASJC Scopus subject areas

    • Physics and Astronomy(all)
    • Condensed Matter Physics

    Cite this

    Magnetically dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions. / Uzdensky, Dmitri A.; MacFadyen, Andrew I.

    In: Physics of Plasmas, Vol. 14, No. 5, 056506, 2007.

    Research output: Contribution to journalArticle

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