TSI Seminar

Forming truncated accretion disks around black holes

Gibwa Musoke

CITA

Forming truncated accretion disks around black holes abstract: Black hole X-ray binaries (and Active Galactic Nuclei) transition through a series of accretion states in a well-defined order. The accretion states, each associated with different luminosities, spectral characteristics and outflow properties, are thought to be triggered by physical changes in the accretion disk around the central black hole. An initially hot and thick accretion disk is thought to transition into a disk that is cool and thin, though the mechanisms behind this transition remain highly debated.

The hard intermediate accretion state present in the midst of a state transition is thought to be associated with the presence of both a hot, thick component– termed the corona, along with a cool and thin component of the accretion flow. The details concerning the geometry of the disk in the hard intermediate state are not agreed upon and numerous models have been proposed: In the “truncated disk” model, the accretion flow is thick and hot close to the black hole, while the outer regions of the flow are thin and cool. There are many open questions concerning the nature of truncated accretion disks: Which mechanisms generate the truncated disk structure? What sets the radius at which the disk truncates? How is the corona formed and what is its geometry? In this talk I present the first high-resolution 3D General Relativistic Magneto-Hydrodynamic (GRMHD) simulations modelling the self-consistent formation of a truncated accretion disk around a black hole.