このエントリーをはてなブックマークに追加
ID 34772
file
creator
Hiragi, Kazuyoshi
Yamazaki, Syoko
Mizuno, Motohiro
Hayashi, Kazuma
Hayashi, Katsuhiro
Nishino, Sho
Ohno, Masanori
subject
galaxies: active
galaxies: individual (Centaurus A)
galaxies: Seyfert
X-rays: galaxies
NDC
Astronomy. Space sciences
abstract
We observed a nearby radio galaxy, Centaurus A (Cen A), three times with Suzaku in 2009 and measured the wide-band X-ray spectral variability more accurately than previous measurements. The Cen A was in an 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 power-law model plus a reflection component, or a power law with a partial covering Compton-thick absorption. The difference spectra between high and low flux periods in each observation were reproduced by a power law with a partial covering Compton-thick absorption. Such a Compton-thick partial covering absorber was observed for the first time in Cen A. The power-law photon index of the difference spectra in 2009 is almost the same as that of the time-averaged spectra in 2005, but steeper by similar to 0.2 than that of the time-averaged spectra in 2009. This suggests an additional hard power-law 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 Large Area Telescope.
journal title
The Astrophysical Journal
volume
Volume 743
issue
Issue 2
start page
124
date of issued
2011
publisher
IOP Publishing Ltd
issn
0004-637X
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
(c) 2011. The American Astronomical Society. All rights reserved.
relation url
department
Graduate School of Science