A Long Observation of NGC 5548 by BeppoSAX: the High Energy Cut-off,   Intrinsic Spectral Variability and a Truly Warm Absorber
  NGC 5548 was observed by BeppoSAX in a single long (8 day) observation from 0.2 to 200 keV. We find (1) the spectral variation of the source is produced by a change of the intrinsic power law slope; (2) a high energy cut-off at $E_c= 115^{+39}_{-27}$ keV with a hint of change of $E_c$ with flux; (3) OVII and OVIII absorption K edges, and a possible blended OVII-OVIII K$\alpha,\beta$ emission feature at $0.54^{+0.07}_{-0.06}$ keV, inconsistent with a purely photoionized gas in equilibrium. We propose that the temperature of the absorbing and emitting gas is $\sim 10^6$ K so that both collisional ionization and photoionization contribute. 
F. Nicastro (1,2,3), L. Piro (1), A. De Rosa (1), M. Feroci (1), P.   Grandi (1), F. Fiore (3), M. Elvis (2), F. Haardt (4),...