Elena Marchese, Valentina Braito, Roberto Della Ceca, Alessandro Caccianiga, Paola Severgnini
We present a detailed analysis of the X-ray spectrum of the Seyfert 2 galaxy
NGC454E, belonging to the interacting system NGC454. Observations performed
with Suzaku, XMM-Newton and Swift allowed us to detect a dramatic change in the
curvature of the 2-10 keV spectrum, revealing a significant variation of the
absorbing column density along the line of sight (from ~ 1 x10^{24}cm^{-2} to ~
1x10^{23}cm^{-2}). Consequently, we propose this source as a new member of the
class of "changing look" AGN, i.e. AGN that have been observed both in
Compton-thin (NH =10^{23 cm^{-2}) and reflection dominated states
(Compton-thick, NH >10^{24} cm^{-2}). Due to the quite long time lag (6 months)
between the Suzaku and XMM-Newton observations we cannot infer the possible
location of the obscuring material causing the observed variability. In the 6-7
keV range the XMM-Newton observation also shows a clear signature of the
presence of an ionized absorber. Since this feature is not detected during the
Suzaku observation (despite its detectability), the simplest interpretation is
that the ionized absorber is also variable; its location is estimated to be
within ~10^{-3} pc from the central black hole, probably much closer in than
the rather neutral absorber.
View original:
http://arxiv.org/abs/1201.2169
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