The origin of UV-optical variability in AGN and its relationship to X-ray variability
Abstract
The origin of UV-optical variability in AGN remains a major puzzle. Is it driven by some process intrinsic to the accretion disc or by reprocessing of X-rays? If driven by reprocessing, what is doing the reprocessing, a surrounding accretion disc or surrounding gas? Measurement of the lags between the various X-ray, UV and optical bands, and of their relative amplitudes of variability, for a sample of AGN of differing black hole mass and accretion rate, can provide strong constraints on the emission scenarios. For AGN with large mass black holes the lags, assuming disc reprocessing, are of order a day and require intensive monitoring for periods of 1-2 months. Swift may carry out one or 2 such programmes per year. However for lower mass AGN where the expected lags are of order an hour, XMM-Newton, using the OM as well as Epic and in combination with ground based optical observations, can obtain excellent lag measurements with only one or two orbits per AGN. I report on one such programme here. It would therefore be possible, with a large programme, for XMM-Newton to measure lags in a sample of AGN and thus greatly extend our understanding of AGN UV-optical variability.
- Publication:
-
XMM-Newton: The Next Decade
- Pub Date:
- June 2016
- Bibcode:
- 2016xnnd.confE...4M