CfA Colloquium Schedule Fall 2004
 16 December 2004

16 December 2004

Speaker: Arieh Konigl (University of Chicago)

Title: Relativistic Jets in Gamma-Ray Burst Sources and Active Galactic Nuclei

Abstract: There is a growing recognition that magnetic fields play a dominant role in driving the collimated relativistic outflows that give rise to gamma-ray bursts (GRBs) and their afterglows. Using exact semianalytic solutions of the ``hot'' special-relativistic ideal-MHD equations, I demonstrate that a strongly magnetized accretion disk (with a dominant polodial or azimutal magnetic field) around a solar-mass black hole can efficiently accelerate a proton-electron outflow to the Lorentz factors and kinetic energies inferred in GRB sources. I discuss the role of thermal pressure (due to radiation and electron-positron pairs) in the initial acceleration of the flow and comment on possible nonideal-MHD effects. I point out some of the implications of this scenario, among which is the possibility that magnetic driving can significantly alleviate the ``baryon contamination'' problem in GRBs if the jet is initially neutron rich. I then apply the insight gained from modeling GRB outflows to the interpretation of relativistic jets in active galactic nuclei. In particular, I argue that the observational indications that these jets are accelerated over distances that far exceed the scale of the central black hole imply that the acceleration is predominantly magnetic. I present preliminary results of a comprehensive model of superluminal jets that could be used to test this interpretation.

Video of the Presentation (Talks can be viewed with RealPlayer. Free download is available from )

References for students:

  1. Vlahakis, N. and Konigl, A.: ``Magnetohydrodynamics of Gamma-Ray Burst Outflows,'' 2001, ApJ, 563, L129
  2. Vlahakis, N., Peng, F. and Konigl, A.: ``Neutron-Rich Hydromagnetic Outflows in Gamma-Ray Burst Sources,'' 2003, ApJ, 594, L23
  3. Vlahakis, N. and Konigl, A.: ``Magnetic Driving of Relativistic Outflows in Active Galactic Nuclei. I. Interpretation of Parsec-Scale Accelerations,'' 2004, ApJ, 605, 656


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