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A Long Observation of NGC 5548 by BeppoSAX: the High Energy Cut-off, Intrinsic Spectral Variability and a Truly Warm Absorber

F. Nicastro·L. Piro·A. De Rosa·M. Feroci·P. Grandi·F. Fiore·M. Elvis·F. Haardt·J. Kaastra·A. Malizia·L. Maraschi·G. Matt·G. C. Perola·P. O. Petrucci
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Abstract

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$α,β$ 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.

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F. Nicastro, L. Piro, A. De Rosa, M. Feroci, P. Grandi, F. Fiore, M. Elvis, F. Haardt, J. Kaastra, A. Malizia, L. Maraschi, G. Matt, G. C. Perola, P. O. Petrucci. 2000-01-12. A Long Observation of NGC 5548 by BeppoSAX: the High Energy Cut-off, Intrinsic Spectral Variability and a Truly Warm Absorber. https://doi.org/10.1086/308950

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