Zusammenfassung
We consider the conditions within Gamma-Ray Burst (GRB) emission region that
is Poynting flux dominated. Due to the enormous magnetic energy density,
relativistic electrons will cool in such a region extremely rapidly via
synchrotron. As there is no known mechanism that can compete with synchrotron
it must be the source of the prompt sub-MeV emission. This sets strong limits
on the size and Lorentz factor of the outflow. Furthermore, synchrotron cooling
is too efficient. It overproduces optical and X-ray as compared with the
observations. This overproduction of low energy emission can be avoided if the
electrons are re-accelerated many times (\$510^4\$) during each
pulse (or are continuously heated) or if they escape the emitting region before
cooling down. We explore the limitations of both models, practically ruling out
the later and demonstrating that the former requires two different acceleration
mechanisms as well as an extremely large magnetic energy to Baryonic energy
ratio. To be viable, any GRB model based on an emission region that is Poynting
flux dominated must demonstrate how these conditions are met. It is more likely
that jets that are launched as magnetically dominated dissipate somehow most of
their magnetic energy before the emission region.
Nutzer