A brief review of long-term X-ray and optical variability in radio-quiet AGN
Abstract
Description
Long-time-scale X-ray and optical variability is a key characteristic of AGN. Here, we summarise our current understanding of the X-ray and optical continuum variability of radio-quiet AGN and the relation between the two bands. We demonstrate the strong connection between the X-ray variability properties of AGN and the variability of stellar-mass black hole candidates on much shorter time-scales, and discuss the implications of this result for the origins of the variability. The relationship between optical and X-ray variability is complex, with some AGN showing strong X-ray/optical correlations while others show no obvious correlation. We suggest a possible explanation for this variety of behaviour.
8 pages, invited contribution to the conference 'Stellar mass, Intermediate-mass and Supermassive black holes', October 28-31 2003, Kyoto, Japan (proceedings to be published in Progress of Theoretical Physics)
8 pages, invited contribution to the conference 'Stellar mass, Intermediate-mass and Supermassive black holes', October 28-31 2003, Kyoto, Japan (proceedings to be published in Progress of Theoretical Physics)