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Date and Time of the Query: 2019-06-18 T07:38:10 PDT
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For refcode 2012ApJ...744...13B:
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2012ApJ...744...13B NGC 5548: Lack of a Broad Fe K{alpha} Line and Constraints on the Location of the Hard X-Ray Source Brenneman, L. W.; Elvis, M.; Krongold, Y.; Liu, Y.; Mathur, S. Abstract. We present an analysis of the co-added and individual 0.7-40 keV spectra from seven Suzaku observations of the Sy1.5 galaxy NGC 5548 taken over a period of eight weeks. We conclude that the source has a moderately ionized, three-zone warm absorber, a power-law continuum, and exhibits contributions from cold, distant reflection. Relativistic reflection signatures are not significantly detected in the co-added data, and we place an upper limit on the equivalent width of a relativistically broad Fe K{alpha} line at EW <= 26 eV at 90% confidence. Thus NGC 5548 can be labeled as a "weak" type 1 active galactic nucleus (AGN) in terms of its observed inner disk reflection signatures, in contrast to sources with very broad, strong iron lines such as MCG-6-30-15, which are likely much fewer in number. We compare physical properties of NGC 5548 and MCG-6-30-15 that might explain this difference in their reflection properties. Though there is some evidence that NGC 5548 may harbor a truncated inner accretion disk, this evidence is inconclusive, so we also consider light bending of the hard X-ray continuum emission in order to explain the lack of relativistic reflection in our observation. If the absence of a broad Fe K{alpha} line is interpreted in the light-bending context, we conclude that the source of the hard X-ray continuum lies at radii r_s_ >~ 100 r_g_. We note, however, that light-bending models must be expanded to include a broader range of physical parameter space in order to adequately explain the spectral and timing properties of average AGNs, rather than just those with strong, broad iron lines. Key words: accretion, accretion disks, galaxies: active, galaxies: individual: NGC 5548, galaxies: nuclei, X-rays: galaxies
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