TY - JOUR
T1 - Magnetically dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions
AU - Uzdensky, Dmitri A.
AU - MacFadyen, Andrew I.
N1 - Funding Information:
D.A.U.’s research has been supported by the National Science Foundation under Grant No. PHY-0215581 (PFC: Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas). A.I.M. acknowledges support from the Keck Fellowship at the Institute for Advanced Study.
PY - 2007
Y1 - 2007
N2 - 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.
AB - 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.
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U2 - 10.1063/1.2721969
DO - 10.1063/1.2721969
M3 - Article
AN - SCOPUS:34249870590
SN - 1070-664X
VL - 14
JO - Physics of Plasmas
JF - Physics of Plasmas
IS - 5
M1 - 056506
ER -