SIMBAD references

We present the results of a 3 year monitoring campaign of the Seyfert 1 galaxy Markarian 509, using X-ray data from the Rossi X-Ray Timing Explorer and optical data taken by the SMARTS consortium. Both light curves show significant variations and are strongly correlated with the optical flux leading the X-ray flux by 15 days. The X-ray power spectrum shows a steep high-frequency slope of -2.0, breaking to a slope of -1.0 at a timescale of 34 days. The lag from optical to X-ray emission is most likely caused by variations in the accretion disk propagating inward.