Changing look: from Compton-thick to Compton-thin, or the re-birth of fossil AGN

Abstract

We discuss the properties of a small sample of Seyfert 2 galaxies whose X-ray spectrum changed appearance on time scales of years, becoming reflection-dominated from Compton-thin, or viceversa. 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 explaining mismatches between optical and X-ray classifications, and provide new strong and direct evidence of the presence of more than one cold circumnuclear region in Seyfert 2 galaxies.

accepted for publication in MNRAS

References in corpus (2)

• Unabsorbed Seyfert 2 galaxies
• Chandra and XMM-Newton observations of Tololo 0109-383

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