Long-term optical and X-ray variability of the Seyfert galaxy Markarian 79 |
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| Authors: | E Breedt P Arévalo I M McHardy P Uttley S G Sergeev T Minezaki Y Yoshii C M Gaskell E M Cackett K Horne S Koshida |
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| Institution: | School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ;Crimean Astrophysical Observatory, P/O Nauchny, Crimea 98409, Ukraine;Isaac Newton Institute of Chile, Crimean Branch, Crimea 98409, Ukraine;Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan;Research Centre for the Early Universe, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;Department of Astronomy, University of Texas, Austin, TX 78712-0259, USA;Chandra Fellow, Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109, USA;School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS;Department of Astronomy, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan |
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| Abstract: | 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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| Keywords: | galaxies: active galaxies: individual: Mrk 79 galaxies: Seyfert |
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