A XMM-Newton monitoring of a candidate changing-look Compton thick AGN

Studies of heavily obscured active galactic nuclei (AGN) suggest that the torusthat causes the obscuration is patchy, rather than uniform. The lineofsightcolumn density (NH_los) of the obscuring material should vary over weeks tomonths, but such an evidence has been observed only in a few Xray detected AGN,due to lack of large samples of heavily obscured AGN with multiepochobservations. We propose for a XMM monitoring of NGC 1358, a nearby Comptonthick (CT) AGN with small torus covering factor and NH_los significantly largerthan the torus average column density. Through this monitoring, we expect tomeasure significant variability in NH_los and detect a transition from CT toCompton thin, thus improving our knowledge on the properties of the obscuring material surrounding AGN. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]