On the role of relativistic effects in the X-ray variability of AGN Piotr Życki Nicolaus Copernicus Astronomical Center, Warsaw, POLAND Andrzej Niedźwiecki Andrzej Niedźwiecki Łódź University, Department of Physics, Łódź, POLAND

Relativistic effects in X-ray spectra Broad Iron Kα line observed in many sources: AGN, X- ray binaries (with black holes and neutron stars). The line is broad because the accretion disk is rotating. What if the X-ray source rotated?

Short-term effects of rotation of an X-ray source Modulation of the primary emission on the orbital time scale Życki & Niedźwiecki 2005

Quasi-periodic signal in power spectra expected… Życki & Niedźwiecki 2005

…but not seen in MCG— Vaughan et al. 2003

However, periodic modulation of the line was observed in NGC 3516 Iwasawa,Miniutti & Fabian 2004 Can be modelled with a co-rotating flare model

Puzzling aspects of long-term (hours-days) X-ray variability of AGN Variability of the reprocessing features (mainly the Fe Kα line) is weaker than, and uncorrelated with, the variability of the primary emission.

The light-bending model ρ = 2 Rg Assumptions: Intrinsic source luminosity is constant. Variability due to change of position of the source, and related change of strength of relativistic effects. Variations of the observed flux and the flux seen by the disk are not correlated, because of relativistic effects. Source averaged over the azimuthal angle (a ring really). Miniutti & Fabian 2004

Line profiles Good fits to the observed line profiles are obtained for small height of the source h= R g h=8 R g (superposition) ( ρ = 2 R g ) h≈0.07 r, r=2-3 R g i=30 o

Line vs continuum variability Model with ρ=2, varying height (M&F) Source just above the disk, changing radial position Source close to the axis Source just above the disk, changing radial position. Luminosity follows dissipation rate. i=30 o

So, the light-bending model for AGN … … can work, in the geometry of radial motion of X-ray sources, low above the disk. The questions are: How fundamental this is (does it apply to all source accreting at high Mdot?) What is the physical mechanism?

High inclination sources i=63 o Model with ρ=2, varying height (M&F) Source just above the disk, changing radial position Source close to the axis The model works in broader range of parameters (height)