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Long-term optical and X-ray variability of the Seyfert galaxy Markarian 79

Breedt, E., Arévalo, P., McHardy, I.M., Uttley, P., Sergeev, S.G., Minezaki, T., Yoshii, Y., Gaskell, C.M., Cackett, E.M., Horne, K. and Koshida, S. (2009) Long-term optical and X-ray variability of the Seyfert galaxy Markarian 79 Monthly Notices of the Royal Astronomical Society, 394, (1), pp. 427-437. (doi:10.1111/j.1365-2966.2008.14302.x).

Record type: Article


We present the results of concurrent X-ray and optical monitoring of the Seyfert 1 galaxy Mrk 79 over a period of more than 5 yr. We find that on short to medium time-scales (days to a few tens of days) the 2–10 keV X-ray and optical u- and V-band fluxes are significantly correlated, with a delay between the bands consistent with 0 d. We show that most of these variations may be well reproduced by a model where the short-term optical variations originate from reprocessing of X-rays by an optically thick accretion disc. The optical light curves, however, also display long time-scale variations over thousands of days, which are not present in the X-ray light curve. These optical variations must originate from an independent variability mechanism and we show that they can be produced by variations in the (geometrically) thin disc accretion rate as well as by varying reprocessed fractions through changes in the location of the X-ray corona.

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Published date: March 2009
Keywords: galaxies: active, galaxies: individual: Mrk 79, galaxies: Seyfert


Local EPrints ID: 144539
ISSN: 0035-8711
PURE UUID: c5b45d2c-ead4-44bf-a9e3-f99e7bfec40e

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Date deposited: 24 May 2010 11:50
Last modified: 18 Jul 2017 23:08

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Author: E. Breedt
Author: P. Arévalo
Author: I.M. McHardy
Author: P. Uttley
Author: S.G. Sergeev
Author: T. Minezaki
Author: Y. Yoshii
Author: C.M. Gaskell
Author: E.M. Cackett
Author: K. Horne
Author: S. Koshida

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