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Ubiquitous Column Density Variability in Seyfert 2 Galaxies

Published online by Cambridge University Press:  05 March 2013

G. Risaliti ,
M. Elvis  and
F. Nicastro
G. Risaliti
Affiliation:
Ossevatorio Astrofisico di Arcetri, Largo E. Fermi, 5, I-50125 Firenze, Italy; risaliti@@arcetri.astro.it Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
M. Elvis
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
F. Nicastro
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
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Abstract

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We present a study of X-ray column density variability in Seyfert 2 galaxies. We show that variations in NH are observed in almost all the objects with multiple hard X-ray observations. Variation timescales (as short as a few months in several cases) are not in agreement with the standard scenario of a parsec-scale toroidal absorber. We propose that the X-ray absorber in Seyfert galaxies is located much nearer to the centre than previously assumed, on the broad line region scale. An extension of the model by M. Elvis (2000) can explain the observed variability. We also show preliminary results of NH variability search inside single X-ray observations, which suggest that variations can occur on timescales of a few 104 s.

Keywords

galaxies: activegalaxies: SeyfertX-rays: galaxies
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 19 , Issue 1 , 2002 , pp. 155 - 157
Copyright
Copyright © Astronomical Society of Australia 2002

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