X-ray Eclipse of the AGN in NGC 1365: Measuring the Source Size

I present a study of the extraordinary X-ray absorption variability of the obscured Seyfert Galaxy NGC 1365. A Chandra campaign of six short observations within ten days revealed an eclipse of the X-ray source in two days. Furthermore, an analysis of the spectral variability in a 60 ks long XMM-Newton observation, when the source was in a Compton-thin state, revealed a transition of an obscuring cloud with N_H ∼ 3×10(23) cm(-2) in ∼ 60 ks. These observations constrain the X-ray source size to < 10(14) cm and the distance of the obscuring cloud to < 10(16) cm.