We discuss the properties of a small sample of type 2 Seyfert galaxies whose X-ray spectra changed appearance on time-scales of years, becoming reflection-dominated from Compton-thin, or vice versa. A reflection-dominated spectrum is usually taken as evidence of Compton-thick absorption, but we instead argue that such a spectrum is due to a temporary switching-off of the nuclear radiation. The observations discussed here may help to explain mismatches between optical and X-ray classifications, and provide new strong and direct evidence for the presence of more than one cold circumnuclear region in type 2 Seyfert galaxies.
Matt, G., Guainazzi, M., Maiolino, R. (2003). Changing look: from Compton-thick to Compton-thin, or the rebirth of fossil active galactic nuclei. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 342(2), 422-426 [10.1046/j.1365-8711.2003.06539.x].
Changing look: from Compton-thick to Compton-thin, or the rebirth of fossil active galactic nuclei
MATT, Giorgio;
2003-01-01
Abstract
We discuss the properties of a small sample of type 2 Seyfert galaxies whose X-ray spectra changed appearance on time-scales of years, becoming reflection-dominated from Compton-thin, or vice versa. A reflection-dominated spectrum is usually taken as evidence of Compton-thick absorption, but we instead argue that such a spectrum is due to a temporary switching-off of the nuclear radiation. The observations discussed here may help to explain mismatches between optical and X-ray classifications, and provide new strong and direct evidence for the presence of more than one cold circumnuclear region in type 2 Seyfert galaxies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
