The dynamics of relativistic magnetized mass loaded outflows carrying toroidal magnetic field is analyzed in the context of Pulsar Wind Nebulae (PWNs). Mass loading is very efficient in slowing down super-relativistic magnetized flows and weakening of relativistic shocks. We suggest that weakening of relativistic reverse shocks by mass loading in PWNs is responsible for the low radiative effici...

We derive the maximum accelerated particle energy from first-order and second-order Fermi acceleration at nonrelativistic and relativistic shocks for explosions taking place in a uniform surrounding medium. Second-order stochastic processes in relativistic flows are shown to be capable of accelerating cosmic rays to ultra-high energies. Cosmic rays above the knee of the cosmic ray spectrum can ...

Rapid variability of the TeV emission in several blazars implies a central black hole mass MBH < 10M⊙, appreciably smaller than the values estimated from the MBH −Lbulg relation, and Doppler factors for the γ-ray emitting fluid much larger than those associated with radio patterns. We discuss the conditions in the central engine required to account for the short timescales and large luminositie...

We investigate relativistic flows after a shock wave generated in a star arrives at the surface. First, the sphericity effect is involved through a successive approximation procedure by adding correction terms to an already known self-similar solution in the ultra-relativistic limit assuming the plane parallel geometry. It is found that the lowest order correction terms are of the order of (a/R...

A property common to several different astrophysical sources of high-energy gamma-rays is the presence of bulk motion at relativistic speed. The intrinsic spectra of the nonthermal radiating particles also show interesting similarities, with a pronounced hardening towards lower energies. This suggests two distinct acceleration mechanisms could be at work in these sources. At high energies, the ...

Aims. We investigate the linear stability properties of the plane interface separating two relativistic magnetized flows in relative motion. The two flows are governed by the (special) relativistic equations for a magnetized perfect gas in the infinite conductivity approximation. Methods. By adopting the vortex-sheet approximation, the relativistic magnetohydrodynamics equations are linearized ...

We propose a variable Eddington factor, depending on the flow velocity v, for the relativistic radiative flow, whose velocity becomes of the order of the speed of light. When the gaseous flow is radiatively accelerated up to the relativistic regime, the velocity gradient becomes very large in the direction of the flow. As a result, the radiative diffusion may become anisotropic in the comoving ...