The relationship between the X-ray and optical variability can give us important clues about the interaction and relationship between physically separated part of the system. Our long term optical monitoring programme of a sample of AGN have revealed a correlation between the short timescale (~days) X-ray and optical variations in these galaxies, suggesting that the optical emission results from X-ray reprocessing by the accretion disc.

However, in addition, there are long-term (several years) variations in the optical light curve, which does not occur in the X-ray lightcurve. These long timescale variations may be accounted for by allowing the disc accretion rate or the geometry of the system to vary over timescales of months - years.

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