The 2009 Fermi Symposium

Constraining GRB Jet Composition with Fermi Data

Bing Zhang

Abstract:

The smooth Band function spectrum of GRB 080916C significantly constrains the composition of the GRB ejecta. In particular, the lack of a thermal emission component expected from the fireball photosphere suggests that the ejecta was not launched as a "fireball" from the central engine. The outflow has to be Poynting-flux dominated at the central engine, and very likely in the emission region as well. A new model for GRB prompt emission in the Poynting-flux dominated regime is proposed.