主要内容:
早期碰撞的慢速磁重连加速喷流，晚期快速无碰撞磁重连产生伽马暴辐射。
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文章信息:
- · arXiv e-print (arXiv:1011.1904)
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| Title: |
| A Reconnection Switch to Trigger Gamma-Ray Burst Jet Dissipation |
| Authors: |
| McKinney, Jonathan C.; Uzdensky, Dmitri A. |
| Publication: |
| eprint arXiv:1011.1904 |
| Publication Date: |
| 11/2010 |
| Origin: |
| ARXIV |
| Keywords: |
| Astrophysics - High Energy Astrophysical Phenomena |
| Comment: |
| 43 pages, 13 figures, submitted to MNRAS on Nov 1, 2010, comments welcome |
| Bibliographic Code: |
| 2010arXiv1011.1904M |
Abstract
Prompt gamma-ray burst (GRB) emission requires some mechanism to dissipate an ultrarelativistic jet. Internal shocks or some form of electromagnetic dissipation are candidate mechanisms. Any mechanism needs to answer basic questions, such as what is the origin of variability, what radius does dissipation occur at, and how does efficient prompt emission occur. These mechanisms also need to be consistent with how ultrarelativistic jets form and stay baryon pure despite turbulence and electromagnetic reconnection near the compact object and despite stellar entrainment within the collapsar model. We use the latest magnetohydrodynamical models of ultrarelativistic jets to explore some of these questions in the context of electromagnetic dissipation due to the slow collisional and fast collisionless reconnection mechanisms, as often associated with Sweet-Parker and Petschek reconnection, respectively. For a highly magnetized ultrarelativistic jet and typical collapsar parameters, we find that significant electromagnetic dissipation may be avoided until it proceeds catastrophically at large radii ($r\sim 10^{13}$--$10^{14}{\rm cm}$), by which the jet has obtained a high Lorentz factor ($\gamma\sim 100$--$1000$), is able to produce non-thermal or quasi-thermal emission while also being optically thin to very high-energy photons, has a gamma-ray luminosity of $L_\gamma \sim 10^{50}$--$10^{51}\ergs$, has observer variability timescales of order $1$s (ranging from $0.001$-$10$s), achieves $\gamma\theta_j\sim 10$--$20$ (for opening half-angle $\theta_j$) so able to produce jet breaks, and has potentially $5-10$ times more energy available for the prompt emission than for the afterglow emission. [abridged]
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