Rapid NH changes in NGC 4151

  title={Rapid NH changes in NGC 4151},
  author={Simonetta Puccetti and Fabrizio Fiore and G. Risaliti and M. Capalbi and Martin Elvis and F. Nicastro . Inafoa Roma and Asi Science Data Center and INAF-IRA Firenze and HarvardCfA and Unam},
  journal={Monthly Notices of the Royal Astronomical Society},
  • S. Puccetti, F. Fiore, +7 authors Unam
  • Published 1 December 2006
  • Physics
  • Monthly Notices of the Royal Astronomical Society
We have analysed the two longest (elapsed time 3d )BeppoSAX observations of the X-ray brightest Seyfert galaxy, NGC 4151, to search for spectral variability on time-scales from a few tens of kiloseconds to years. We found in both cases highly significant spectral variability below ≈6 keV down to the shortest time-scales investigated. These variations can be naturally explained in terms of variations in the low energy cut-off due to obscuring matter along the line of sight. If the cut-off is… 
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