X-ray timing of Active Galaxies
Abstract
The rapid and seemingly random fluctuations in X-ray luminosity of Seyfert galaxies provided early support for the standard model in which Seyferts are powered by a supermassive black hole fed from an accretion disc. However, in the years following EXOSAT there was little opportunity to advance our understanding of the most rapid X-ray variability. Observations with XMM-Newton have changed this.
We discuss the impact of XMM-Newton timing results on our understanding of Seyfert galaxies. Particular attention will be given to the remarkable similarity found been the timing properties of Seyferts and black hole X-ray binaries, including the power spectrum, cross spectrum (time delays and coherence), and the ubiquitous rms-flux relation. These results strong support the hypothesis of 'Black Hole Unification': If strong gravity dominates the dynamics of the inner accretion flow around black holes then scale invariance implies accretion onto super-massive black holes AGN should be fundamentally the same as for stellar mass black holes in Galactic Black Hole (GBH) X-ray binaries, with the dynamical frequencies scaling inversely with the black hole mass. We will also discuss why current AGN data have not shown strong evidence for quasi-periodic oscillations (QPOs), despite their presence in GBHs, and detail the technological and methodological problems in this search.- Publication:
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AAS/High Energy Astrophysics Division #9
- Pub Date:
- September 2006
- Bibcode:
- 2006HEAD....9.1004V