Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-02-20
Astrophys.J.647:1192-1212,2006
Astronomy and Astrophysics
Astrophysics
19 pages, 8 figures, accepted to ApJ, updated references and additional discussion added
Scientific paper
10.1086/505621
We propose a magnetic mechanism for the collimated explosion of a massive star relevant for GRBs, XRFs and asymmetric supernovae. We apply Lynden-Bell's magnetic tower scenario to the interior of a massive rotating star after the core has collapsed to form a black hole with an accretion disk or a millisecond magnetar acting as a central engine. We solve the force-free Grad-Shafranov equation to calculate the magnetic structure and growth of a tower embedded in a stellar environment. The pressure of the toroidal magnetic field, continuously generated by differential rotation of the central engine, drives a rapid expansion which becomes vertically collimated after lateral force balance with the surrounding gas pressure is reached. The collimation naturally occurs because hoop stress concentrates magnetic field toward the rotation axis and inhibits lateral expansion. This leads to the growth of a self-collimated magnetic tower. When embedded in a massive star, the supersonic expansion of the tower drives a strong bow shock behind which an over-pressured cocoon forms. The cocoon confines the tower by supplying collimating pressure and provides stabilization against disruption due to MHD instabilities. Because the tower consists of closed field lines starting and ending on the central engine, mixing of baryons from the cocoon into the tower is suppressed. The channel cleared by the growing tower is thus plausibly free of baryons and allows the escape of magnetic energy from the central engine through the star. While propagating down the stellar density gradient, the tower accelerates and becomes relativistic. During the expansion, fast collisionless reconnection becomes possible resulting in dissipation of magnetic energy which may be responsible for GRB prompt emission.
MacFadyen Andrew I.
Uzdensky Dmitri A.
No associations
LandOfFree
Stellar Explosions by Magnetic Towers does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Stellar Explosions by Magnetic Towers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stellar Explosions by Magnetic Towers will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-520135