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| Paper: |
The MHD Origin of GRBs: A New View at the GRB Proper--Afterglow Correlations |
| Volume: |
312, Third Rome Workshop on Gamma-Ray Bursts in the Afterglow Era |
| Page: |
369 |
| Authors: |
Kazanas, D.; Contopoulos, J. |
| Abstract: |
Based on the exact solution of the axisymmetric dipole magnetosphere and its asymptotic split-monopole configuration we propose a model for the GRB central engine along the lines suggested sometime ago by Usov, namely a highly magnetized (B ~ 1015 G), rapidly spinning (P ~ 1 msec) neutron star. As discussed by us (Contopoulos & Kazanas 2002), the asymptotic solution of a spinning axisymmetric dipole leads to a quasispherical MHD wind which gradually converts its Poynting flux to a relativistic motion, with its Lorentz factor Γ proportional to the wind radius R. The acceleration saturates at a value Γ0 at radius R0, when its intertial energy density becomes comparable to that of the magnetic field. Further increase in the Lorentz factor is averted by a change in the wind geometry which collimates away from its initial conical shape. We propose that the ensuing development of this wind through the ISM constitutes the GRB and its afterglow. We speculate that the variety of GRB properties depends, mainly, on the magnitude of the cross section π R20 of the collimated winds, with the broader ones having the larger Lorentz factors Γ0. Since larger Γ0 leads to a brighter GRB, while larger π R20 to a shorter afterglow break time, the correlations between the properties of the GRB proper and their afterglows are qualitatively obtained. |
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