Gamma-ray flares of blazars

Krzysztof Nalewajko

May 23, 2013

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Abstract: Blazars are one of the most important cosmic sources of gamma-ray radiation. They are characterized by persistent and stochastic variability, occasionally leading to powerful flares. It is accepted that this radiation is produced in relativistic jets pointing to us from supermassive black holes of active galactic nuclei. However, it is not established what physical processes are involved, and even the distance scale remains controversial. I will describe recent observational progress made possible by the Fermi Space Telescope and ground-based Cerenkov observatories. I will discuss how well we can constrain the parameters of gamma-ray emitting regions, and what can we learn from the most extreme events. Finally, I will argue for a significant role of current-driven instabilities and relativistic magnetic reconnection in powering the gamma-ray flares of blazars.