Black holes come in a variety of sizes — from a mass of a few Suns, to millions or even billions of solar masses. As these vastly different black holes feast on accreting matter, do they behave in the same way?
An example model in cross-section of the possible geometry of an accreting black hole before and after a state transition. The two emitting components are the hot coronal gas enveloping the black hole and the thin accretion disk that lies at its midplane. [Adapted from Ruan et al. 2019]When a black hole feeds, it emits a lot of light: from the accreting disk of material that swirls around its midplane, from the hot corona of gas surrounding the black hole, and sometimes from fast-moving jets emitted from its poles. These different components all have different temperatures, which means their light peaks at different wavelengths. This means that we can use the shape of a black hole’s spectrum to learn about the physical geometry of an accreting black hole system.
Feasting black holes don’t always maintain the same geometry, though! Black holes transition between different states over time — each with its own physical geometry and spectrum shape. ...