Open AccessChanging look: from Compton‐thick to Compton‐thin, or the rebirth of fossil active galactic nuclei
Author(s) -
Matt Giorgio,
Guainazzi Matteo,
Maiolino Roberto
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06539.x
Subject(s) - physics , astrophysics , galaxy , compton scattering , active galactic nucleus , spectral line , reflection (computer programming) , astronomy , absorption (acoustics) , radiation , optics , photon , computer science , programming language
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.