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

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 cleanmore » 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.« less

Authors:
;  [1];  [2]
  1. Department of Astrophysical Sciences, Princeton University, and Center for Magnetic Self-Organization (CMSO), Princeton, New Jersey 08544 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20975079
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2721969; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BLACK HOLES; COSMIC GAMMA BURSTS; EXPLOSIONS; INTERACTIONS; MAGNETIC FIELDS; MAGNETISM; MAGNETOHYDRODYNAMICS; NICKEL 56; PLASMA; PULSARS; STELLAR ATMOSPHERES; SUPERNOVAE

Citation Formats

Uzdensky, Dmitri A., MacFadyen, Andrew I., and Department of Physics, New York University, New York, New York 10003 and Institute for Advanced Study, Princeton, New Jersey 08540. Magnetically dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions. United States: N. p., 2007. Web. doi:10.1063/1.2721969.
Uzdensky, Dmitri A., MacFadyen, Andrew I., & Department of Physics, New York University, New York, New York 10003 and Institute for Advanced Study, Princeton, New Jersey 08540. Magnetically dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions. United States. doi:10.1063/1.2721969.
Uzdensky, Dmitri A., MacFadyen, Andrew I., and Department of Physics, New York University, New York, New York 10003 and Institute for Advanced Study, Princeton, New Jersey 08540. Tue . "Magnetically dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions". United States. doi:10.1063/1.2721969.
@article{osti_20975079,
title = {Magnetically dominated jets inside collapsing stars as a model for gamma-ray bursts and supernova explosions},
author = {Uzdensky, Dmitri A. and MacFadyen, Andrew I. and Department of Physics, New York University, New York, New York 10003 and Institute for Advanced Study, Princeton, New Jersey 08540},
abstractNote = {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.},
doi = {10.1063/1.2721969},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}