Chandra monitoring of UGC 4203: the structure of the X-ray absorber

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 2 weeks. This is the third, clear case, after NGC 1365 and NGC 7582, of dramatic N<sub>H</sub> variability on short time-scales observed in a `changing look' source, i.e. an active galactic nuclei (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 centre 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.