Patterns and Coincidences in the Light Curves of Active Galaxies

Abstract

We draw attention to some intriguing coincident patterns in the optical light curves of NGC 4151 and NGC 5548. Inspecting the light curves of these two classic Seyferts, we find evidence for at least five occurrences of a similar sequence of variations. This pattern consists of a ~ 2 yr long sequence of shorter flares, with a total energy of 3--5 10^{50} ergs in the B-band. We predict that the on-going monitoring campain on NGC 5548 should soon reveal more occurrences of this general pattern if it is truly recurrent. We speculate on the possibility that this pattern is associated with a fundamental/universal `unit' of variability in active galaxies, and discuss a possible connection with the variability properties of QSOs.

8 pages, uuencoded, gzip'ed, tar-file [Patterns.tar.gz.uu, 340Kb] Uses mn.sty, epsf.sty Also available at http://www.if.ufrgs.br/~cid MNRAS, accepted (March/1997)

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