Suzaku view of X-ray Spectral Variability of the Radio Galaxy Centaurus A : Partial Covering Absorber, Reflector, and Possible Jet Component

Abstract

We observed a nearby radio galaxy, the Centaurus A (Cen A), three times with Suzaku in 2009, and measured the wide-band X-ray spectral variability more accurately than the previous measurements. The Cen A was in the active phase in 2009, and the flux became higher by a factor of 1.5--2.0 and the spectrum became harder than that in 2005. The Fe-K line intensity increased by 20--30% from 2005 to 2009. The correlation of the count rate between the XIS 3--8 keV and PIN 15--40 keV band showed a complex behavior with a deviation from a linear relation. The wide-band X-ray continuum in 2--200 keV can be fitted with an absorbed powerlaw model plus a reflection component, or a powerlaw with a partial covering Compton-thick absorption. The difference spectra between high and low flux periods in each observation were reproduced by a powerlaw with a partial covering Compton-thick absorption. Such a Compton-thick partial covering absorber was for the first time observed for the Cen A. The powerlaw photon index of the difference spectra in 2009 is almost the same as that of the time-averaged spectra in 2005, but steeper by $\sim 0.2$ than that of the time-averaged spectra in 2009. This suggests an additional hard powerlaw component with a photon index of $<1.6$ in 2009. This hard component could be a lower part of the inverse-Compton-scattered component from the jet, whose gamma-ray emission has recently been detected with the Fermi/LAT.

43 pages, 16 figures, will appear in the ApJ

References in corpus (12)

• An XMM-Newton survey of broad iron lines in Seyfert galaxies
• Bright AGN Source List from the First Three Months of the Fermi Large Area Telescope All-Sky Survey
• Swift BAT Survey of AGN
• Fermi Gamma-ray Imaging of a Radio Galaxy
• The X-ray nuclei of intermediate-redshift radio sources
• High-energy particle acceleration at the radio-lobe shock of Centaurus A
• The central parsecs of Centaurus A: High Excitation Gas, a Molecular Disk, and the Mass of the Black Hole
• Chandra and XMM-Newton Observations of the Nucleus of Centaurus A
• The Suzaku Observation of the Nucleus of the Radio-Loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material
• Spectral variability of GX 339-4 in a hard-to-soft state transition
• Integral-field spectroscopy of Centaurus A nucleus
• Evidence for Non-Hydrostatic Gas Motions in the Hot ISM of Centaurus A

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• Constraints on Physical Conditions for the Acceleration on Ultra-high-energy Cosmic Rays in Nearby Active Galactic Nuclei Observed with the Fermi Large Area Telescope
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