CEA astronomers discover a supermassive black hole that is brighter than it should be!

The nuclei of active galaxies and quasars are powered by the vast amounts of energy released as material spirals down in a disc towards a supermassive black hole in the center of a host galaxy. This energy heats the matter up to high temperatures, so it is intensely luminous, with its emission peaking close to the black hole event horizon. Pour more material in, get more luminosity out is the general rule, but there is a limit to how luminous this material can be. This is called the Eddington limit, and it marks the point where the radiation is so bright that its outward pressure is bigger than the inward pull of gravity. Its long been a puzzle as to what happens if the mass accretion rate through the outer disc means that the inner disc is brighter than this limit. Here, the data from ESA's XMM-Newton satellite shows what happens. This satellite has optical and UV telescopes, which see the emission from the outer disc, co-aligned with an X-ray telescope, which sees the emission from the inner disc. The mass accreting through the outer disc is at least 12x bigger than the Eddington limit for the inner disc. So if nothing happened to the disc structure we should see a luminosity which is 12x bigger than Eddington. But we don't - we see a luminosity which is 'only' 5x Eddington! The difference in power must go somewhere - either into blowing part of the material away as a wind, or by being directly capture by the black hole (or both!). So this is direct observational evidence that the disc structure changes around the Eddington limit, as well as direct evidence that supermassive black holes can go (a bit!) brighter than just the Eddington limit.

Link to the original research paper: http://arxiv.org/abs/1706.08125

Contacts from CEA, Durham:

Chris Done

Martin Ward

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