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 $E_c= 115^{+39}_{-27}$keVwithahintofchangeof$E_c$ with flux; (3) OVII and OVIII absorption K edges, and a possible blended OVII-OVIII K$\alpha ,\beta$ emission feature at $0.54_{-0.06}^{+0.07}$ 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.