Mapping the extreme environments around black holes

42nd COSPAR Assembly, Pasadena, CA (20/07/2018)

From the reflection and reverberation of X-rays from the innermost regions of AGN accretion discs, a three-dimensional picture is starting to emerge of the structure of the disc and the corona producing the intense X-ray emission, as well of how the launching sites of jets may be connected to the corona and inner disc. 

Spectral timing analysis of AGN observed by the great X-ray observatories, compared to the predictions of general relativistic ray tracing simulations, reveals not only the mechanisms of variability in the X-ray emission, but enables the structure of the corona and accretion disc to be mapped. We discover how the corona evolves on long and short timescales, giving rise to orders of magnitude variation in luminosity as well as the processes the corona can undergo during transient events, most notably the collimation and ejection of portions of the corona during X-ray flares, reminiscent of the aborted launching of a jet.

The latest X-ray reverberation studies are revealing, for the first time, structure within the corona including a persistent collimated core akin to the base of a jet, even in radio-quiet sources, alongside a second component associated with the accretion disc itself.

This gives us important insight into the small-scale processes close to the event horizon that enable supermassive black holes to power some of the most luminous objects in the Universe, launch vast jets at close to the speed of light and play their important feedback role in the formation of structure in the Universe.