We report the spectral analysis of a long XMM-Newton observation of the well-studied, moderate luminosity broad line Seyfert 1 galaxy NGC 5548. The source was at an historically average brightness and we find the hard (3-10 keV) spectrum can be well fitted by a power law of photon index Gammasimilar to1.75, together with reflection. The only feature in the hard X-ray spectrum is a narrow emission line near 6.4 keV, with an equivalent width of similar to60 eV. The energy and strength of this line are consistent with fluorescence from 'neutral' iron distant from the central continuum source. We find no evidence for a broad Fe K line, with an upper limit well below previous reports, suggesting the inner accretion disc is now absent or highly ionized. The addition of simultaneous BeppoSAX data allows the analysis to be extended to 200 keV, yielding important constraints on the total reflection. Extrapolation of the hard X-ray power law down to 0.3 keV shows a clear 'soft excess' below similar to0.7 keV. After due allowance for the effects of a complex warm absorber, measured with the XMM-Newton RGS, we find that the soft excess is better described as a smooth upward curvature in the continuum flux below similar to2 keV. The soft excess can be modelled either by Comptonized thermal emission or by enhanced reflection from the surface of a highly ionized disc.
Pounds, K.a., Reeves, J.n., Page, K.l., Edelson, R., Matt, G., Perola, G.c. (2003). A simultaneous XMM-Newton and BeppoSAX observation of the archetypal broad line Seyfert 1 galaxy NGC 5548. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 341(3), 953-960 [10.1046/j.1365-8711.2003.06470.x].
A simultaneous XMM-Newton and BeppoSAX observation of the archetypal broad line Seyfert 1 galaxy NGC 5548
MATT, Giorgio;
2003-01-01
Abstract
We report the spectral analysis of a long XMM-Newton observation of the well-studied, moderate luminosity broad line Seyfert 1 galaxy NGC 5548. The source was at an historically average brightness and we find the hard (3-10 keV) spectrum can be well fitted by a power law of photon index Gammasimilar to1.75, together with reflection. The only feature in the hard X-ray spectrum is a narrow emission line near 6.4 keV, with an equivalent width of similar to60 eV. The energy and strength of this line are consistent with fluorescence from 'neutral' iron distant from the central continuum source. We find no evidence for a broad Fe K line, with an upper limit well below previous reports, suggesting the inner accretion disc is now absent or highly ionized. The addition of simultaneous BeppoSAX data allows the analysis to be extended to 200 keV, yielding important constraints on the total reflection. Extrapolation of the hard X-ray power law down to 0.3 keV shows a clear 'soft excess' below similar to0.7 keV. After due allowance for the effects of a complex warm absorber, measured with the XMM-Newton RGS, we find that the soft excess is better described as a smooth upward curvature in the continuum flux below similar to2 keV. The soft excess can be modelled either by Comptonized thermal emission or by enhanced reflection from the surface of a highly ionized disc.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
