Rapid N_H Changes in NGC 4151

Abstract

We have analyzed two long BeppoSAX observations of the bright Seyfert galaxy NGC 4151, searching for short timescale (10-200 ksec) X-ray spectral variability. The light curve of a softness ratio, chosen as most sensitive to pinpoint changes of the column density of the absorbing gas along the line of sight, shows significant variations. We try to model these variations by performing a detailed, time resolved, spectral analysis. We find significant, large (factors of 1.5-6) variations of the absorber column densities on time scales of 40-200 ksec. These values are 10-100 times shorter than those found by Risaliti et al. 2002 in a sample of Seyfert 2 galaxies, and provide strong constraints on the geometry of the obscuring medium.

To appear in Proc. of the BeppoSAX Symposium: "The Restless High-Energy Universe", E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers (Eds)

References in corpus (3)

• Ubiquitous variability of X-ray absorbing column densities in Seyfert 2 Galaxies
• NGC 4151: an intrinsically average Seyfert 1
• The broad Fe K line profile in NGC 4151

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• XMM-Newton observations of the Lockman Hole V: time variability of the brightest AGN
• The Suzaku Observation of NGC 3516: Complex Absorption and the Broad and Narrow Fe K Lines
• A Near Infrared View of Nearby Galaxies: The Case of NGC 6300
• The XMM deep survey in the CDF-S. X. X-ray variability of bright sources
• Swift Observations of the highly X-ray variable Narrow Line Seyfert 1 galaxy RX J0148.3-2758
• X-ray Unveiling Events in a z~1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South
• A (likely) X-ray jet from NGC6217 observed by XMM-Newton