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Preprint 06/01

QUASI­PERIODIC OSCILLATION IN SEYFERT GALAXIES: SIGNIFICANCE LEVELS. THE CASE OF MARKARIAN 766

Sara Benlloch (1), Jörn Wilms (1), Rick Edelson (2), Tahir Yaqoob (3,4), and Rüdiger Staubert (1)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Department of Astronomy, University of California at Los Angeles, Los Angeles, CA 90095­1562.
(3) Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, MD 20771.
(4) Department of Physics and Astronomy, Johns Hopkins University, Homewood Campus, 3400 North Charles Street, Baltimore, MD 21218.

2001, The Astrophysical Journal 562, L121 - L124

Abstract. We discuss methods to compute significance levels for the existence of quasi­periodic oscillations (QPOs) in active galactic nuclei (AGNs) that take the red­noise character of the X­ray light curves of these objects into account. Applying epoch folding and periodogram analysis to the XMM­Newton observation of the Seyfert galaxy Mrk 766, a possible QPO at a timescale of 4200 s has been reported. Our computation of the significance of this QPO, however, shows that the 4200 s peak is not significant at the 95% level. We conclude that the 4200 s feature is an artifact of the red­noise process and not the result of a physical process within the AGNs.

Key words: accretion, accretion disks - galaxies: individual (Markarian 766) - galaxies: Seyfert - X­rays: galaxies

Paper (115k gzip'ed Postscript including figures)

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