Title : Heating of the Compact X-ray Corona in Seyfert Galaxies
Speaker Name: Dr. Yajie Yuan
Speaker Institution : Princeton University
Notes: Coffee and snacks available at 3 PM.
Abstract : There is observational evidence that the X-ray continuum source that creates the broad fluorescent emission lines in some Seyfert Galaxies may be compact and located at a few gravitational radii above the black hole. We consider two scenarios for the X-ray emission. The first possibility is that the X-rays may be produced by particles accelerated in an electrostatic gap at the base of a putative jet. However, our detailed study of the gap kinetic physics and scaling suggests that the energetics is not enough in these environments. The second possibility is that the compact X-ray emitting source may be powered by small scale flux tubes near the black hole that are attached to the orbiting accretion disk. Our force-free simulations show that the field linking the black hole and the disk can get twisted up by the differential rotation to form a magnetic tower. When the confinement provided by the field from the outer disk is strong, the built-up magnetic tower can quickly become kink unstable, which leads to continuous reconnection and dissipates most of the energy extracted from the rotating black hole. This could in principle power a hot X-ray emitting region above the black hole.