February 11
Resolving the innermost regions around supermassive black holes
Speaker: Prof. Dan Wilkins, Ohio State University
Abstract: "X-ray reflection from the innermost regions of the accretion disk provides a unique probe of the extreme environment just outside the event horizon of a black hole. X-rays emitted by a region of particle acceleration close to the black hole known as the corona illuminate the inner disk revealing a wealth of information about these processes, and the properties of the innermost regions of the accretion flow and the black hole itself.
The high-resolution X-ray spectrometer on board XRISM, along with recent advances in the measurement of not just X-ray reflection, but also X-ray reverberation, where variations in the X-ray emission are seen to echo off of the inner accretion disk, are revolutionising our ability to resolve detailed structure of the inner accretion disk and corona.
These measurements are giving us new insight into the physics behind rapid black hole growth and AGN feedback, as accreting black holes release vast amounts of energy into their environments via radiation, jets and winds. A lot remains unknown about the fundamental processes by which they were able to grow rapidly in the early Universe and the impact they have on their host galaxies during these phases of rapid black hole growth. I will discuss how high-resolution X-ray spectroscopy and measurements of reflection and reverberation form the inner accretion disk are revealing the connection between the inner accretion disk and the launching of ultrafast winds and jets, and how X-ray reverberation mapping is providing new measurements of the structure of accretion flows that approach or exceed the Eddington limit. "
Host: Dr. Chris Reynolds