Rapid Compton-thick/Compton-thin Transitions in the Seyfert 2 Galaxy NGC 1365

Abstract

We present multiple Chandra and XMM-Newton observations of the type 1.8\nSeyfert Galaxy NGC 1365, which shows the most dramatic X-ray spectral changes\nobserved so far in an AGN: the source switched from reflection dominated to\ntransmission dominated and back in just 6 weeks. During this time the soft\nthermal component, arising from a ~1 kpc region around the center, remained\nconstant. The reflection component is constant at all timescales, and its high\nflux relative to the primary component implies the presence of thick gas\ncovering a large fraction of the solid angle. The presence of this gas, and the\nfast variability time scale, suggest that the Compton-thick to Compton thin\nchange is due to variation in the line-of-sight absorber, rather than to\nextreme intrinsic emission variability. We discuss a structure of the\ncircumnuclear absorber/reflector which can explain the observed X-ray spectral\nand temporal properties.\n