Galactic and extragalactic X-ray transients, theory and observational perspectives

Theoretical studies have shown that the multi-wavelength emission of the nuclei of active galaxies, stellar mass black hole and neutron star binaries is fueled by their accretion disks. The accretion process may be not stationary, and the accretion history as well as geometric structure of the infalling matter are not well understood. Importantly, the magnetic fields must play a key role in sustaining the accretion flows. While we have progressed in understanding many of these phenomena, there are recent observations and new models that drive our understanding in new directions. They are related either to the instabilities in the innermost part of the disk or to the sudden interaction of circumnuclear stars with the central black hole and the disk. Processes close to the black hole also allow testing of General Relativity in a strong field regime.

Topics: Quasi periodic eruptions in accreting black holes, Tidal disruption events, Changing activity of supermassive black holes, Fast variability of Galactic X-ray sources, Accretion instabilities and gravitational waves from black hole and neutron star binaries, Testing General Relativity with supermassive black holes