Journal Article

Relativistic iron K X-ray reverberation in NGC 4151

A. Zoghbi, A. C. Fabian, C. S. Reynolds and E. M. Cackett

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 422, issue 1, pages 129-134
Published in print May 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI:
Relativistic iron K X-ray reverberation in NGC 4151

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Recent X-ray observations have enabled the study of reverberation delays in active galactic nuclei (AGN) for the first time. All the detections so far are in sources with a strong soft excess, and the measured delay is between the hard (1–3 keV) direct continuum and the soft excess (0.5–1 keV), interpreted as the reflection continuum smeared by relativistic effects. There is however an inherent ambiguity in identifying and studying the details of the lines in the soft excess. Here we report the first detection of reverberation in the iron K band in any AGN. Using XMM–Newton observations of NGC 4151, we find delays of the order of 2000 s on time-scales of 105 s between the  keV band and the and  keV bands, with a broad lag profile resembling a relativistically broadened iron line. The peak of the lag spectra shifts to lower energies at higher frequencies, consistent with the red wing of the line being emitted at smaller radii, as expected from reflection off the inner accretion disc. This is a first detection of a broad iron line using timing studies.

Keywords: galaxies: active; galaxies: nuclei; galaxies: Seyfert; X-rays: galaxies

Journal Article.  4286 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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