期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 342, 期 2, 页码 422-426出版社
OXFORD UNIV PRESS
DOI: 10.1046/j.1365-8711.2003.06539.x
关键词
galaxies : active; galaxies : Seyfert; X-rays : galaxies
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.
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