Dissipation efficiency of reconfinement shocks in relativistic jets

Abstract

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 ∈ 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 ? 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. © 2012 The Author. Monthly Notices of the Royal Astronomical Society © 2012 RAS.