NGC 454: unveiling a new ‘changing look’ active galactic nucleus

摘要: We present a detailed analysis of the X-ray spectrum Seyfert 2 galaxy NGC 454E, belonging to interacting system 454. Observations performed with Suzaku, XMM–Newton and Swift allowed us detect dramatic change in curvature 2–10 keV spectrum, revealing significant variation absorbing column density along line sight (from ∼ 1 × 1024 cm−2 1023 cm−2). Consequently, we propose this source as new member class ‘changing look’ active galactic nuclei (AGN), i.e. AGN that have been observed both Compton thin (NH= 1023  cm−2) reflection-dominated states (Compton thick, NH > 1024  cm−2). Due quite long time lag (six months) between Suzaku observations, cannot infer possible location obscuring material causing variability. In 6–7 keV range, observation also shows clear signature presence an ionized absorber. Since feature is not detected during (despite its detectability), simplest interpretation absorber variable; estimated be within 10−3 pc from central black hole, probably much closer than rather neutral