RATOP2020 — Relativistic astrophysics, Theory and observational perspectives

Theoretical studies have shown that the muti-wavelength emission in the nuclei of the active galaxies, and black hole binaries, is fueled by their accretion disks. The magnetic fields therein must mediate the transfer of mass and angular momentum. In addition, shock waves, possibly related to the regions tidally excited by the companion star in a binary system, may influence the accretion process and observed flaring emission. Finally, the episodes of jets being launched from the central engines, in both radio-blazars and in gamma ray bursts, are giving important insight into the physics of black hole accretion, and help estimate the fundamental parameters of the black holes, such as their masses and spins. These effects are studied by advanced numerical simulations, that use the methods of general relativistic magnetohydrodynamics.

Theoretical investigations are verified experimentally through the timing and spectral properties of the observed sources. In the last years, the observational context has been enormously enhanced due to discovery of gravitational waves, which give independent constraints on the masses (and possibly spins) of the merging compact stars. The multi-wavelength detection of accompanying events of the short GRBs, such as the kilonovae, have brought further important information about the conditions within the post-merger environment. Finally, the fundamental theories of gravity can be tested now with unprecedented precision through the signals from compact objects, such as quasars, supernovae, and gravitational-wave sources.

Topics: active galaxies, black holes, accretion, magnetic fields, jets, general relativity, gravitational waves