S E M I N A R IDepartament d'Astronomia i Astrofísica
Universitat de València
Particle acceleration in GRB and AGN
Max-Planck-Institut für Kernphysik, Heidelberg, Alemanya
Seminari del Departament d'Astronomia i Astrofísica
Dilluns 31 maig 2004
The process or processes which accelerate the particles responsible for the nonthermal emission observed in gamma-ray bursts and active galactic nuclei are still unknown. However, the only proposed mechanism with significant predictive power is the first-order Fermi process operating at a shock front. In nonrelativistic flows, this mechanism has been applied in a wide variety of astrophysical situations and has been the subject of considerable theoretical effort. The relativistic outflow from a gamma-ray burst or AGN, on the other hand, demands a different approach, able to account for the intrinsic anisotropy of the particle distribution functions. I will briefly review the theory, contrasting the non-relativistic and relativistic cases, and present some new calculations of test-particle acceleration in the presence of shock-generated magnetic field. I will then discuss the application to models of GRB and AGN spectra, stressing an analogy with the relativistic termination shock of the wind from the Crab pulsar.