II. Time-resolved spectroscopy
Dept. of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA e-mail: firstname.lastname@example.org
2 Astrophysics Science Division, NASA/GSFC, Greenbelt, MD 20771, USA
3 Dept. of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
4 Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
5 Department of Physics, Catholic University of America, Washington DC 20064, USA
Accepted: 10 August 2007
Context.The variable X-ray spectra of AGN systematically show steep power-law high states and hard-spectrum low states. The hard, low state has previously been found to be a component with only weak variability. The origin of this component and the relative importance of effects such as absorption and relativistic blurring are currently not clear.
Aims.In a follow-up of previous principal components analysis we aim to determine the relative importance of scattering and absorption effects on the time-varying X-ray spectrum of the narrow-line Seyfert 1 galaxy Mrk 766.
Methods.Time-resolved spectroscopy, slicing XMM and Suzaku data down to 25 ks elements is used to investigate whether absorption or scattering components dominate the spectral variations in Mrk 766.
Results.Time-resolved spectroscopy confirms that spectral variability in Mrk 766 can be explained by either of two interpretations of principal components analysis. Detailed investigation confirm rapid changes in the relative strengths of scattered and direct emission or rapid changes in absorber covering fraction provide good explanations of most of the spectral variability. However, a strong correlation between the 6.97 keV absorption line and primary continuum together with rapid opacity changes show that variations in a complex and multi-layered absorber, most likely a disk wind, are the dominant source of spectral variability in Mrk 766.
Key words: galaxies: Seyfert / X–rays: galaxies
Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA, also on observations obtained with Suzaku, a collaboration between ISAS/JAXA and NASA/GSFC, MIT.
© ESO, 2007