The connection between radio-quiet active galactic nuclei and the high/soft state of X-ray binaries.

A large sample of active galactic nuclei (AGN) studied here shows a ‘quenching’ of the radio emission that occurs when the luminosity is from a few per cent to about 10 per cent of the Eddington rate, just as is seen in the high/soft state of X-ray binaries. The result holds even when the sample of AGN includes no narrow line Seyfert 1 galaxies (the systems most commonly suggested to be the analogue of the high/soft state). This adds substantially to the body of evidence that AGN show the same spectral state phenomenology and related disc–jet coupling as the stellar mass accreting black holes. That the power-law correlation between X-ray and radio luminosity is the same in both AGN and X-ray binaries and extends below 10−7 LEDD strengthens the argument that there is no fundamental difference between the low/hard state and the so-called quiescent state in X-ray binaries. We also discuss possible reasons for the scatter in the radio to X-ray luminosity correlation in the AGN. [ABSTRACT FROM AUTHOR]