19 March 2025: Fergus Baker

Speaker: Fergus Baker (Bristol)

Date: Wednesday 19 March 2025

Time: 15:00

Location: 3.21

Black holes and their crowns

Accreting black holes observed with X-ray telescopes have characteristic spectra with two key components. The first is a lower-energy, multi-temperature black-body representing thermal emission from the accretion disc. The other is a higher-energy power-law component, thought to originate from the so-called black hole X-ray corona. Many properties of these coronae are still widely debated, including their formation mechanisms, their geometrical properties, and how they interact with the surrounding accreting material. Part of the difficulty is that the standard forward-modelling approaches used by X-ray astronomers run into intense computational complexity when attempting to simulate geometrically extended coronae. Consequently, the majority of results are obtained using an admittedly unphysical but tractable point-like corona. In this talk, I will examine the challenges that have enveloped spectral models involving a corona. I will explain how these models are constructed, discuss our recent advancements in modelling geometrically extended coronae, and show some of our illustrative results.