
TY  - JOUR
A1  - Risaliti, G. 
A1  - Elvis, M. 
A1  - Nicastro, F. 
T1  - Ubiquitous Column Density Variability in Seyfert 2 Galaxies
JF  - Publications of the Astronomical Society of Australia
JO  - Publ. Astron. Soc.  Aust.
Y1  - 2002
VL  - 19
IS  - 1
SP  - 155
EP  - 157
KW  - galaxies: active &#8212; galaxies: Seyfert &#8212; X-rays: galaxies
UR  - https://doi.org/10.1071/AS01116 
N2  - 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 &#40;as short as a few months in several cases&#41; 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 &#40;2000&#41; 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. 
ER  -

