EDP Sciences
Free access
Issue
A&A
Volume 387, Number 2, May IV 2002
Page(s) 714 - 724
Section Physical and chemical processes
DOI http://dx.doi.org/10.1051/0004-6361:20020390


A&A 387, 714-724 (2002)
DOI: 10.1051/0004-6361:20020390

Acceleration of GRB outflows by Poynting flux dissipation

G. Drenkhahn

Max-Planck-Institut für Astrophysik, Postfach 1317, 85741 Garching bei München, Germany

(Received 21 December 2001 / Accepted 11 March 2002)

Abstract
We study magnetically powered relativistic outflows in which a part of the magnetic energy is dissipated internally by reconnection. For GRB parameters, and assuming that the reconnection speed scales with the Alfvén speed, significant dissipation can take place both inside and outside the photosphere of the flow. The process leads to a steady increase of the flow Lorentz factor with radius. With an analytic model we show how the efficiency of this process depends on GRB parameters. Estimates are given for the thermal and non-thermal radiation expected to be emitted from the photosphere and the optically thin part of the flow respectively. A critical parameter of the model is the ratio of Poynting flux to kinetic energy flux at some initial radius of the flow. For a large value ( $\ga$100) the non-thermal radiation dominates over the thermal component. If the ratio is small ( $\la$40) only prompt thermal emission is expected which can be identified with X-ray flashes.


Key words: gamma rays: bursts -- magnetic fields -- magnetohydrodynamics (MHD) -- stars: winds, outflows




© ESO 2002

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.