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3.6. AGN variability studies: an agenda for the next millenium?

Published online by Cambridge University Press:  25 May 2016

M.-H. Ulrich
M.-H. Ulrich*
Affiliation:
European Southern Observatory, Karl-Schwarzschild Str. 2, 85748 Garching, Germany

Extract

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Data which are obtained today can be re-acquired better and faster in the future. Their only enduring value, after they have been interpreted, is as historical markers. With electronic archiving one can envision archives covering decades, centuries and even longer periods of observations of selected objects or classes of objects. Such a data base would allow the study of phenomena with low temporal frequencies, and of rare events.

First hints of such phenomena in AGN have been discovered recently: 1) The Seyfert 1s, the best studied AGN at present, exhibit flux variations on time scales ranging from hours to several years (see Ulrich et al. 1997). The faster variations (up to months) have been extensively observed, and they are best understood as being caused by magnetic flares in the corona above the central part of the accretion disk (Blandford and Payne 1982). The origin of the long term and large amplitude UV/optical flux variations (factor 20 in several years as observed in NGC4151 and F9), however, remain essentially unknown.

Type
Part I. Stellar Cluster, Star Formation
Information
Symposium - International Astronomical Union , Volume 184: The Central Regions of the Galaxy and Galaxies , 1998 , pp. 99 - 101
Copyright
Copyright © Kluwer 1998 

References

Blandford, R.D. and Payne, D.G., 1982, MNRAS, Vol. 199, pp. 883–903.Google Scholar
Falcke, H., Wilson, A.S. and Ho, L.C., 1997, Relativistic Jets in AGN, Cracow 1997, Ostrowski, M. et al eds., in press.Google Scholar
Genzel, R., et al., 1997, MNRAS, in press, MPE preprint 413.Google Scholar
Ho, L.C., Filippenko, A.V. and Sargent, W.L.W., 1995, Ap. J. Suppl. Ser, Vol. 98, pp. 477–593.Google Scholar
Ho, L.C., Filippenko, A.V. and Sargent, W.L.W., 1995, Ap. J, Vol. 462, pp. 183–202.Google Scholar
Maoz, D., et al., 1995, Ap. J, Vol. 440, pp. 91–99.Google Scholar
Mezger, P., 1994, “The Nuclei of Normal Galaxies”, p. 415, Genzel, R. and Harris, A.I. (eds), Kluwer Acad. Publishers.Google Scholar
Pounds, K.A., et al., 1995, MNRAS, Vol. 277, pp. L5–L10.Google Scholar
Renzini, A., et al., 1995, Nature, Vol. 378, pp. 39–41.Google Scholar
Storchi-Bergmann, T., et al., 1995, Ap. J, Vol. 443, pp. 617–624.Google Scholar
Ulrich, M.-H., Maraschi, L. and Urry, C.M., 1997, ARAA, Vol. 35, pp. 445–502.Google Scholar