2012MNRAS.420L..48N

We calculate the dissipation efficiency of relativistic reconfinement shocks. Building on previous work, we consider different distributions of the external pressure. The average dissipation efficiency ε_diss is a function of the product of two parameters - the jet Lorentz factor Γ_j and the reconfinement angle Θ_r, which is related to the opening angle Θ_j and the external pressure index η. The spatial distribution of the dissipation rate strongly depends on η. We discuss the significance of these results for the properties of relativistic jets in gamma-ray bursts and active galactic nuclei and propose that reconfinement shocks may explain a very high dissipation efficiency of the former and a moderate dissipation efficiency of the latter. Finally, we estimate the dissipation efficiency of the reconfinement shock associated with the quasi-stationary knot HST-1 in the jet of radio galaxy M87 and show that it is roughly consistent with the observational constraints.