Ubiquitous Variability of X‐Ray–absorbing Column Densities in Seyfert 2 Galaxies
Ubiquitous Variability of X‐Ray–absorbing Column Densities in Seyfert 2 Galaxies
We present a study of the variations in the absorbing column density of 25 X-ray-defined Seyfert 2 galaxies, as inferred from hard X-ray observations, on timescales from months to several years. We show that a significant variation of NH (from 20% to 80%) is observed in almost all (22 of …