Speaker
Description
Rapid variability over a large range of wavelengths is a defining feature of blazars and radio galaxies. The shortest time scales are observed at the highest gamma-ray energies, with significant flux variations over a few days or hours not uncommon, while the most extreme events reach the minute time scale. The origin of the underlying processes is not well known, but most scenarios place the emission region inside the relativistic jets, where rapid flares can be caused by macroscopic effects or by transient particle acceleration and emission processes. Particle acceleration can occur in shocks or turbulences, but might also be due to magnetic reconnection, depending on the physical conditions of the emission region. Quite possibly there is more than a single process at play behind the variety of observed flare shapes and their different time scales.
I will provide a short overview of the main types of models trying to explain rapid flare emission in such sources, with a focus on their predictions of light-curve shapes, spectra and intrinsic time delays.