Dissipation Efficiency of Reconfinement Shocks in Relativistic Jets
  We calculate the dissipation efficiency of relativistic reconfinement shocks.
Building on previous work (Nalewajko & Sikora 2009), we consider different
distributions of the external pressure. The average dissipation efficiency
epsilon_diss is a function of the product of two parameters - the jet Lorentz
factor Gamma_j and the reconfinement angle Theta_r, which is related to the
opening angle Theta_j and the external pressure index eta. The spatial
distribution of the dissipation rate strongly depends on eta. 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.
