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Paper: NGC 4051: a Disappearing Warm Absorber
Volume: 159, BL Lac Phenomenon
Page: 27
Authors: Orr, A.; Barr, P.; Guainazzi, M.; Parmar, A.
Abstract: Among the most prominent observational signatures of the partly ionized component in active galactic nuclei (AGN), the so-called warm absorber, are spectral absorption features detected in the keV region. These features provide important diagnostics on the location and nature of the material surrounding the active nucleus. The Low Energy Concentrator Spectrometer (LECS) on board the BeppoSAX satellite operates in the range 0.1--10 keV. Because of its good low-energy resolution and effective area down to 0.1 keV it is a very efficient tool for the study of the complex spectral features due to warm absorbers, particularly when used in combination with the other narrow field instruments on BeppoSAX, sensitive at higher energies. We will present here new constraints on the physical state of the warm absorber in AGN brought by BeppoSAX/LECS observations as well as by recent results from other X-ray observatories.
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