Accretion onto Black Holes

Accretion of gas onto black holes can extract huge amounts of energy and lead to some of the most energetic phenomena in the Universe: active galactic nuclei, X-ray binaries, tidal disruption events or gamma-ray bursts.

TA scientists have been studying black hole accretion flows for many years using state-of-art general relativistic numerical codes which allow us to properly follow the black hole physics and evolution of magnetic fields leading to turbulence.

Very recently, we have developed codes which evolve not only gas and magnetic field, but also radiation, and which can handle both optically thin and thick medium. In this way we are able to self-consistently study thin and slim accretion disk which are supported by radiation pressure.

This ongoing research aims at answering some long-standing and exciting questions related to black hole accretion:
- How accurate are black hole spin estimates based on the thin disk theory?
- Can thin disks exist at very low luminosities?
- What makes X-ray binaries change spectral states?
- Are radiation-pressure dominated disks thermally stable?
- What is the structure of the disk corona?
- What does accretion at super-Eddington rates look like?
- How strong are outflows of mass, energy and momentum from optically thick disks?