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Post Info TOPIC: Phoenix Galaxy


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Posts: 131433
Date:
UGC 4203
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Title: Chandra monitoring of UGC 4203: the structure of the X-ray absorber
Authors: G. Risaliti, M. Elvis, S. Bianchi, G. Matt

We present a Chandra monitoring campaign of the highly variable Seyfert galaxy UGC 4203 (the "Phoenix Galaxy") which revealed variations in the X-ray absorbing column density on time scales of two weeks. This is the third, clear case, after NGC 1365 and NGC 7582, of dramatic N_H variability on short time scales observed in a "changing look" source, i.e. an AGN observed in the past in both a reflection-dominated and a Compton-thin state. The inferred limits on the distance of the X-ray absorber from the center suggest that the X-ray "torus" could be one and the same with the broad emission line region. This scenario, first proposed for an "ad-hoc" picture for NGC 1365, may be the common structure of the circumnuclear medium in AGN.

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Posts: 131433
Date:
Phoenix Galaxy
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Title: Suzaku observation of the Phoenix Galaxy
Authors: G. Matt, S. Bianchi, H. Awaki, A. Comastri, M. Guainazzi, K. Iwasawa, E. Jimenez-Bailon, F. Nicastro

In recent years, several Seyfert 2 galaxies have been discovered that change state when observed in X-rays a few years apart, switching from Compton-thin to reflection-dominated or vice versa. We observed a member of this class of "Changing-look" sources, the Phoenix Galaxy, with Suzaku, with the aim of better understanding the nature of the variations. The Suzaku spectrum was analysed, and the results compared with previous ASCA and XMM-Newton observations. The source was caught in a Compton-thin state, as in XMM-Newton, but differently from ASCA. Comparing the Suzaku and XMM-Newton observations, a variation in the column density of the absorber on a time scale of years is discovered. A similar change, but on much shorter time scales (i.e. ks) may also explain the count-rate variations during the Suzaku observations. A soft excess is also present, likely due to continuum and line emission from photoionised circumnuclear matter.

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