Origin of XRFs: low E, low contrast of Γ or large viewing angle?

摘要

We have developed a toy model for internal shocks which has been used to produce a large number of synthetic GRB/XRF events in order to find the critical parameters for the production of X-ray flashes. The key factor appears to be a small contrast of the Lorentz factor in the relativistic outflow emitted by the central engine.