Grigorios Katsoulakos

Grigorios Katsoulakos  ( Greece )


Nonthermal Processes near Supermassive Black Holes

Supermassive black holes, fed by accreted galactic gas, are widely considered to be hosted at the center of most, if not all, galaxies. This particularly applies to active galaxies where this structure can be radiatively stronger and be accompanied by the presence of a relativistic collimated outflow.
Recent observations at gamma-ray energies have revealed that AGNs can be strong TeV emitters. Their VHE emission is often found to be highly variable (\Delta t of order $\Delta t_BH$ or less). In the case of under-luminous non-blazar AGN, the origin of this emission could potentially be attributed to nonthermal processes taking place within the black hole's magnetosphere (i.e. on scales r < 10 R_s). This fact is also strengthened by observations in radio band. Motivated by previous work, in this project I will investigate a self-consistent description of how particles are accelerated and injected within the jet base. This provides crucial input for advancing our understanding of jet formation and the plasma composition and radiative properties in extragalactic jets. In the frame of this work, the TeV flaring emission is a sub-product of a more general process. Since the mechanism is sensitive to the accretion rate (\dot{m}) at the inner edge of the disk, the effects of general relativity on the disk properties have to be explored. The active galaxies M87 and IC310, as well as the "passive" source SgrA* are ideal astrophysical laboratories where such a model could be applied in order to disclose some of the fundamental physics hidden in these objects.

Supervisor:   Frank Rieger ( ITA/MPIK )

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