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Anatomy of the AGN in NGC 5548 VIII. XMM-Newton's EPIC detailed view of an unexpected variable multilayer absorber | | M. Cappi
; B. De Marco
; G. Ponti
; F. Ursini
; P.-O. Petrucci
; S. Bianchi
; J.S. Kaastra
; G.A. Kriss
; M. Mehdipour
; M. Whewell
; N. Arav
; E. Behar
; R. Boissay
; G. Branduardi-Raymont
; E. Costantini
; J. Ebrero
; L. Di Gesu
; F.A. Harrison
; S. Kaspi
; G. Matt
; S. Paltani
; B.M. Peterson
; K.C. Steenbrugge
; D.J. Walton
; | | Date: |
6 Apr 2016 | | Abstract: | In 2013 we conducted a large multi-wavelength campaign on the archetypical
Seyfert 1 galaxy NGC 5548. Unexpectedly, this usually unobscured source
appeared strongly absorbed in the soft X-rays during the entire campaign, and
signatures of new and strong outflows were present in the almost simultaneous
UV HST/COS data. Here we carry out a comprehensive spectral analysis of all
available XMM-Newton observations of NGC 5548 (for a total of ~763 ks) in
combination with 3 simultaneous NuSTAR obs. We obtain a best-fit composed by i)
a weakly varying flat (Gamma~1.5-1.7) power-law component; ii) a constant, cold
reflection (FeK + continuum) component; iii) a soft excess, possibly due to
thermal Comptonization; and iv) a constant, ionized scattered emission-line
dominated component. Our main findings are that, during the 2013 campaign, the
first 3 of these components appear to be partially covered by a heavy and
variable obscurer located along the l.o.s. that is consistent with a multilayer
of cold and mildly ionized gas. We characterize in detail the short timescale
(~ks-to-days) spectral variability of this new obscurer, and find it is mostly
due to a combination of Nh and Cf variations, on top of intrinsic power-law
variations. In addition, our best-fit spectrum is left with several (but
marginal) absorption features at rest-frame energies ~6.7-6.9 keV and ~8 keV,
as well as a weak broad emission line feature redwards of the 6.4 keV emission
line. These could indicate a more complex underlying model, e.g. a P-Cygni-type
profile if allowing for a large velocity and wide-angle outflow. These findings
are consistent with a picture where the obscurer represents the manifestation
along the l.o.s. of a multilayer of gas that is likely outflowing at high
speed, and simultaneously producing heavy obscuration and scattering in the
X-rays and broad absorption features in the UV. | | Source: | arXiv, 1604.1777 | | Services: | Forum | Review | PDF | Favorites | |
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