Jet break is the rapid, non recurring, change in the optical properties of a jet. In this entry we discuss several possible mechanisms.

Beaming Edit

Jet break due to beaming occurs when the beaming angle of a jet becomes larger than the opening angle

$ \frac{1}{\Gamma} > \theta $

If the jet is adiabatic, then the relation between the jet radius and the Lorentz factor is given by the Blandford McKee solution (assuming uniform density)

$ \Gamma \propto R^{-3/2} $

The arrival time is related to the radius via

$ t_a \approx \frac{R}{\Gamma^2} $

Putting these two equations together yields

$ \Gamma \propto t_a^{-3/8} \Rightarrow t_a \propto \theta^{8/3} $