Breedt, E., Arévalo, P., McHardy, Ian 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, Vol. 394 (No. 1). pp. 427-437. doi:10.1111/j.1365-2966.2008.14302.x

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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.

Item Type:	Journal Article
Divisions:	Faculty of Science > Physics
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley
ISSN:	00358711
Official Date:	2009
Dates:	Date Event 2009 Published
Volume:	Vol. 394
Number:	No. 1
Page Range:	pp. 427-437
DOI:	10.1111/j.1365-2966.2008.14302.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access

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