X-ray absorption variability in NGC 4507
  We present a complete spectral analysis of an XMM-Newton and Chandra campaign of the obscured AGN in NGC 4507, consisting of six observations spanning a period of six months, ranging from June 2010 to December 2010. We detect strong absorption variability on time scales between 1.5 and 4 months, suggesting that the obscuring material consists of gas clouds at parsec-scale distance. The lack of significant variability on shorter time scales suggests that this event is not due to absorption by broad line region clouds, which was instead found in other studies of similar sources. This shows that a single, universal structure of the absorber (either BLR clouds, or the parsec-scale torus) is not enough to reproduce the observed complexity of the X-ray absorption features of this AGN. 
Andrea Marinucci, Guido Risaliti, Junfeng Wang, Stefano Bianchi,   Martin Elvis, Giorgio Matt, Emanuele Nardini, Valentina B...
astro-ph.HE astro-ph.CO